Re: constructor, super, and data members issue
With that line of thinking, the user "should **always** know what they've
done", meaning there's no need to avoid functionality in favor of avoiding
foot-guns. Yet...
As far as assigning a class definition directly to a field, developers
coming to JS/ES from other languages (especially Java) may not think so as
it is fairly common practice in some languages to define one class
completely inside another, but not inside any method of the outer class.
The exposure of such inner classes varies with the need for which it was
written. I wouldn't be so quick to discount this kind of assignment as
"niche". In either case, even if it does turn out to be niche and we ignore
that little restriction, that has little bearing on the potential solution
I've offered. This approach allows the value initializer to live in a
getter for the property on the prototype. The first access to the property
puts the value uniquely onto the instance. The example code isn't perfect,
but it does cover the basic idea. It might be better written like this:
```js
class Example {
//classField = class{}; //Error
otherField=[ "foo", "bar"];
}
class ES6Example {
//classField ignored for this example since it was an error.
get otherField() {
let _otherField_InitialValue_ = [ "foo", "bar" ];
if ((this instanceof ES6Example) &&
!this.hasOwnProperty("otherField") &&
Object.isExtensible(this) &&
Object.getOwnPropertyDefinition(this.__proto__,
"otherField").configurable) {
this.otherField = _otherField_InitialValue_;
}
return _otherField_InitialValue_;
}
}
```
On Tue, Sep 4, 2018 at 12:39 AM Jordan Harband wrote:
> I'd say that defining a class directly in a class field is extremely
> niche, and by doing that, the user "should know what they've done" too.
>
> On Mon, Sep 3, 2018 at 3:44 PM, Ranando King wrote:
>
>> That scenario is intentional. I see no need to ban it. I would only want
>> to ban the confusing case of direct assignment in the outer class
>> declaration. For cases where the user intentionally defines a class as you
>> have done, they should know that what they've done will create a class that
>> is persistently re-defined with each instance. As has been said many times
>> before, it's good to reduce the number of foot-guns, but at some point, you
>> have to expect some level of responsibility from the programmer. Consider
>> that rule as little more than a safety switch.
>>
>> On Mon, Sep 3, 2018 at 3:52 PM Jordan Harband wrote:
>>
>>> `field = (function () { return class { }; }())` - how exactly would you
>>> propose banning creating a class inside class fields?
>>>
>>> On Mon, Sep 3, 2018 at 12:05 PM, Ranando King wrote:
>>>
>>>> I've been thinking about the problems around this some more. At first I
>>>> couldn't get past the dissenting arguments from issue #123, but I've since
>>>> come up with a solution that might work. What if:
>>>>
>>>> * Make it illegal to define a class directly on a class field in a
>>>> class declaration.
>>>> * Move the assignment portion of a class field declaration into a
>>>> getter on the prototype such that the getter sets an own property on the
>>>> instance if it doesn't exist, then returns that value
>>>>
>>>> What I mean is this:
>>>>
>>>> ```js
>>>> class Example {
>>>> //classField = class{}; //Error
>>>> otherField=[ "foo", "bar"];
>>>> }
>>>>
>>>> class ES6Example {
>>>> //classField ignored for this example since it was an error.
>>>> get otherField() {
>>>> if ((this instanceof ES6Example) &&
>>>> !this.hasOwnProperty("otherField"))
>>>> this.otherField = [ "foo", "bar" ];
>>>> return this.otherField;
>>>> }
>>>> }
>>>> ```
>>>>
>>>> Done this way, any code expecting early assignment of a field being
>>>> used as though it were "abstract" will still work as expected.
>>>>
>>>> On Thu, Aug 30, 2018 at 4:38 PM doodad-js Admin
>>>> wrote:
>>>>
>>>>> I'm late to the party, but I've found a solution for my non-loved
>>>>> framework : have another constructor called before "super", which fills a
>>>>> faked "this" and a faked "args" then replicated values to "this" after
>>>>> doing "super(
Re: constructor, super, and data members issue
I'd say that defining a class directly in a class field is extremely niche,
and by doing that, the user "should know what they've done" too.
On Mon, Sep 3, 2018 at 3:44 PM, Ranando King wrote:
> That scenario is intentional. I see no need to ban it. I would only want
> to ban the confusing case of direct assignment in the outer class
> declaration. For cases where the user intentionally defines a class as you
> have done, they should know that what they've done will create a class that
> is persistently re-defined with each instance. As has been said many times
> before, it's good to reduce the number of foot-guns, but at some point, you
> have to expect some level of responsibility from the programmer. Consider
> that rule as little more than a safety switch.
>
> On Mon, Sep 3, 2018 at 3:52 PM Jordan Harband wrote:
>
>> `field = (function () { return class { }; }())` - how exactly would you
>> propose banning creating a class inside class fields?
>>
>> On Mon, Sep 3, 2018 at 12:05 PM, Ranando King wrote:
>>
>>> I've been thinking about the problems around this some more. At first I
>>> couldn't get past the dissenting arguments from issue #123, but I've since
>>> come up with a solution that might work. What if:
>>>
>>> * Make it illegal to define a class directly on a class field in a class
>>> declaration.
>>> * Move the assignment portion of a class field declaration into a getter
>>> on the prototype such that the getter sets an own property on the instance
>>> if it doesn't exist, then returns that value
>>>
>>> What I mean is this:
>>>
>>> ```js
>>> class Example {
>>> //classField = class{}; //Error
>>> otherField=[ "foo", "bar"];
>>> }
>>>
>>> class ES6Example {
>>> //classField ignored for this example since it was an error.
>>> get otherField() {
>>> if ((this instanceof ES6Example) && !this.hasOwnProperty("
>>> otherField"))
>>> this.otherField = [ "foo", "bar" ];
>>> return this.otherField;
>>> }
>>> }
>>> ```
>>>
>>> Done this way, any code expecting early assignment of a field being used
>>> as though it were "abstract" will still work as expected.
>>>
>>> On Thu, Aug 30, 2018 at 4:38 PM doodad-js Admin
>>> wrote:
>>>
>>>> I'm late to the party, but I've found a solution for my non-loved
>>>> framework : have another constructor called before "super", which fills a
>>>> faked "this" and a faked "args" then replicated values to "this" after
>>>> doing "super(...fakedArgs)".
>>>>
>>>> https://github.com/doodadjs/doodad-js/blob/v9.1.3/src/
>>>> common/Bootstrap.js#L5320-L5330
>>>>
>>>> -Original Message-
>>>> From: Isiah Meadows
>>>> Sent: Sunday, August 26, 2018 3:29 PM
>>>> To: Logan Smyth
>>>> Cc: Ben Wiley ; es-discuss <
>>>> es-discuss@mozilla.org>
>>>> Subject: Re: constructor, super, and data members issue
>>>>
>>>> Yeah, I was more focused on the static class side of things, because I
>>>> thought they were referring to that. Class instance fields are different,
>>>> and so of course, those are never set on the prototype unless for whatever
>>>> reason, the parent constructor returns `Object.getPrototypeOf(this)`
>>>> instead of letting it default to the normal `this`.
>>>>
>>>> My bad, and you are correct.
>>>>
>>>> -
>>>>
>>>> Isiah Meadows
>>>> cont...@isiahmeadows.com
>>>> www.isiahmeadows.com
>>>>
>>>> On Sun, Aug 26, 2018 at 12:20 PM Logan Smyth
>>>> wrote:
>>>> >
>>>> > Static class fields run their initializers and define the properties
>>>> > at declaration time, and class constructors have the parent class as
>>>> > the `[[Prototype]]`, so static field values are inherited. I think
>>>> this is adding to confusion though, because while that's absolutely true,
>>>> that is not applicable in the same way to non-static class fields, which is
>>>> what this original email is focused on. You could indeed also address this
>>>> with static properties in a proper ES6 environment as ``` class Base {
>>>> > static idAttribute = "id&
Re: constructor, super, and data members issue
That scenario is intentional. I see no need to ban it. I would only want to
ban the confusing case of direct assignment in the outer class declaration.
For cases where the user intentionally defines a class as you have done,
they should know that what they've done will create a class that is
persistently re-defined with each instance. As has been said many times
before, it's good to reduce the number of foot-guns, but at some point, you
have to expect some level of responsibility from the programmer. Consider
that rule as little more than a safety switch.
On Mon, Sep 3, 2018 at 3:52 PM Jordan Harband wrote:
> `field = (function () { return class { }; }())` - how exactly would you
> propose banning creating a class inside class fields?
>
> On Mon, Sep 3, 2018 at 12:05 PM, Ranando King wrote:
>
>> I've been thinking about the problems around this some more. At first I
>> couldn't get past the dissenting arguments from issue #123, but I've since
>> come up with a solution that might work. What if:
>>
>> * Make it illegal to define a class directly on a class field in a class
>> declaration.
>> * Move the assignment portion of a class field declaration into a getter
>> on the prototype such that the getter sets an own property on the instance
>> if it doesn't exist, then returns that value
>>
>> What I mean is this:
>>
>> ```js
>> class Example {
>> //classField = class{}; //Error
>> otherField=[ "foo", "bar"];
>> }
>>
>> class ES6Example {
>> //classField ignored for this example since it was an error.
>> get otherField() {
>> if ((this instanceof ES6Example) &&
>> !this.hasOwnProperty("otherField"))
>> this.otherField = [ "foo", "bar" ];
>> return this.otherField;
>> }
>> }
>> ```
>>
>> Done this way, any code expecting early assignment of a field being used
>> as though it were "abstract" will still work as expected.
>>
>> On Thu, Aug 30, 2018 at 4:38 PM doodad-js Admin
>> wrote:
>>
>>> I'm late to the party, but I've found a solution for my non-loved
>>> framework : have another constructor called before "super", which fills a
>>> faked "this" and a faked "args" then replicated values to "this" after
>>> doing "super(...fakedArgs)".
>>>
>>>
>>> https://github.com/doodadjs/doodad-js/blob/v9.1.3/src/common/Bootstrap.js#L5320-L5330
>>>
>>> -Original Message-
>>> From: Isiah Meadows
>>> Sent: Sunday, August 26, 2018 3:29 PM
>>> To: Logan Smyth
>>> Cc: Ben Wiley ; es-discuss <
>>> es-discuss@mozilla.org>
>>> Subject: Re: constructor, super, and data members issue
>>>
>>> Yeah, I was more focused on the static class side of things, because I
>>> thought they were referring to that. Class instance fields are different,
>>> and so of course, those are never set on the prototype unless for whatever
>>> reason, the parent constructor returns `Object.getPrototypeOf(this)`
>>> instead of letting it default to the normal `this`.
>>>
>>> My bad, and you are correct.
>>>
>>> -
>>>
>>> Isiah Meadows
>>> cont...@isiahmeadows.com
>>> www.isiahmeadows.com
>>>
>>> On Sun, Aug 26, 2018 at 12:20 PM Logan Smyth
>>> wrote:
>>> >
>>> > Static class fields run their initializers and define the properties
>>> > at declaration time, and class constructors have the parent class as
>>> > the `[[Prototype]]`, so static field values are inherited. I think
>>> this is adding to confusion though, because while that's absolutely true,
>>> that is not applicable in the same way to non-static class fields, which is
>>> what this original email is focused on. You could indeed also address this
>>> with static properties in a proper ES6 environment as ``` class Base {
>>> > static idAttribute = "id";
>>> >
>>> > constructor() {
>>> >this.idAttribute = new.target.idAttribute;
>>> > }
>>> > }
>>> > class Derived extends Base {
>>> > static idAttribute = "_id";
>>> >
>>> > constructor() {
>>> >super();
>>> > }
>>> > }
>>> > ```
>>> >
>>> > On Sun, Aug 26, 2018 at 10:35 AM Isiah Meadows
>>> wrote:
>>> >>
>>> >> Every obj
Re: constructor, super, and data members issue
`field = (function () { return class { }; }())` - how exactly would you
propose banning creating a class inside class fields?
On Mon, Sep 3, 2018 at 12:05 PM, Ranando King wrote:
> I've been thinking about the problems around this some more. At first I
> couldn't get past the dissenting arguments from issue #123, but I've since
> come up with a solution that might work. What if:
>
> * Make it illegal to define a class directly on a class field in a class
> declaration.
> * Move the assignment portion of a class field declaration into a getter
> on the prototype such that the getter sets an own property on the instance
> if it doesn't exist, then returns that value
>
> What I mean is this:
>
> ```js
> class Example {
> //classField = class{}; //Error
> otherField=[ "foo", "bar"];
> }
>
> class ES6Example {
> //classField ignored for this example since it was an error.
> get otherField() {
> if ((this instanceof ES6Example) && !this.hasOwnProperty("
> otherField"))
> this.otherField = [ "foo", "bar" ];
> return this.otherField;
> }
> }
> ```
>
> Done this way, any code expecting early assignment of a field being used
> as though it were "abstract" will still work as expected.
>
> On Thu, Aug 30, 2018 at 4:38 PM doodad-js Admin
> wrote:
>
>> I'm late to the party, but I've found a solution for my non-loved
>> framework : have another constructor called before "super", which fills a
>> faked "this" and a faked "args" then replicated values to "this" after
>> doing "super(...fakedArgs)".
>>
>> https://github.com/doodadjs/doodad-js/blob/v9.1.3/src/
>> common/Bootstrap.js#L5320-L5330
>>
>> -Original Message-
>> From: Isiah Meadows
>> Sent: Sunday, August 26, 2018 3:29 PM
>> To: Logan Smyth
>> Cc: Ben Wiley ; es-discuss <
>> es-discuss@mozilla.org>
>> Subject: Re: constructor, super, and data members issue
>>
>> Yeah, I was more focused on the static class side of things, because I
>> thought they were referring to that. Class instance fields are different,
>> and so of course, those are never set on the prototype unless for whatever
>> reason, the parent constructor returns `Object.getPrototypeOf(this)`
>> instead of letting it default to the normal `this`.
>>
>> My bad, and you are correct.
>>
>> -
>>
>> Isiah Meadows
>> cont...@isiahmeadows.com
>> www.isiahmeadows.com
>>
>> On Sun, Aug 26, 2018 at 12:20 PM Logan Smyth
>> wrote:
>> >
>> > Static class fields run their initializers and define the properties
>> > at declaration time, and class constructors have the parent class as
>> > the `[[Prototype]]`, so static field values are inherited. I think this
>> is adding to confusion though, because while that's absolutely true, that
>> is not applicable in the same way to non-static class fields, which is what
>> this original email is focused on. You could indeed also address this with
>> static properties in a proper ES6 environment as ``` class Base {
>> > static idAttribute = "id";
>> >
>> > constructor() {
>> >this.idAttribute = new.target.idAttribute;
>> > }
>> > }
>> > class Derived extends Base {
>> > static idAttribute = "_id";
>> >
>> > constructor() {
>> >super();
>> > }
>> > }
>> > ```
>> >
>> > On Sun, Aug 26, 2018 at 10:35 AM Isiah Meadows
>> wrote:
>> >>
>> >> Every object, including functions, have an internal prototype.
>> Functions normally have one set to `Function.prototype`, and objects
>> normally inherit from `Object.prototype` at least indirectly. But because
>> of how prototypes work, the only requirement for something to be used as a
>> prototype is that it must be an object. So you can do
>> `Object.create(someFunction)` and although you can't call it (it's not a
>> callable object), that object inherits all the properties and methods from
>> that function. `class` in JavaScript is just sugar over a common pattern
>> (really complex sugar requiring `new.target` to emulate, but still sugar),
>> not an entirely new concept, and it all builds off of prototypes.
>> Specifically, the instance prototype inherits from the parent prototype,
>> and the class constructor itself inherits from the parent constructor.
>> That's why if you declare a static `call` method on a parent class
Re: constructor, super, and data members issue
Even with the suggestion I've made, I would still recommend keeping the
post-super() initialization function. It would simply get all of the class
fields from the prototype. Those that haven't already been initialized
would be, guaranteeing that all fields that need to be initialized would be
by the time they are needed in the code.
On Mon, Sep 3, 2018 at 2:05 PM Ranando King wrote:
> I've been thinking about the problems around this some more. At first I
> couldn't get past the dissenting arguments from issue #123, but I've since
> come up with a solution that might work. What if:
>
> * Make it illegal to define a class directly on a class field in a class
> declaration.
> * Move the assignment portion of a class field declaration into a getter
> on the prototype such that the getter sets an own property on the instance
> if it doesn't exist, then returns that value
>
> What I mean is this:
>
> ```js
> class Example {
> //classField = class{}; //Error
> otherField=[ "foo", "bar"];
> }
>
> class ES6Example {
> //classField ignored for this example since it was an error.
> get otherField() {
> if ((this instanceof ES6Example) && !this.hasOwnProperty("otherField"))
> this.otherField = [ "foo", "bar" ];
> return this.otherField;
> }
> }
> ```
>
> Done this way, any code expecting early assignment of a field being used
> as though it were "abstract" will still work as expected.
>
> On Thu, Aug 30, 2018 at 4:38 PM doodad-js Admin
> wrote:
>
>> I'm late to the party, but I've found a solution for my non-loved
>> framework : have another constructor called before "super", which fills a
>> faked "this" and a faked "args" then replicated values to "this" after
>> doing "super(...fakedArgs)".
>>
>>
>> https://github.com/doodadjs/doodad-js/blob/v9.1.3/src/common/Bootstrap.js#L5320-L5330
>>
>> -Original Message-
>> From: Isiah Meadows
>> Sent: Sunday, August 26, 2018 3:29 PM
>> To: Logan Smyth
>> Cc: Ben Wiley ; es-discuss <
>> es-discuss@mozilla.org>
>> Subject: Re: constructor, super, and data members issue
>>
>> Yeah, I was more focused on the static class side of things, because I
>> thought they were referring to that. Class instance fields are different,
>> and so of course, those are never set on the prototype unless for whatever
>> reason, the parent constructor returns `Object.getPrototypeOf(this)`
>> instead of letting it default to the normal `this`.
>>
>> My bad, and you are correct.
>>
>> -
>>
>> Isiah Meadows
>> cont...@isiahmeadows.com
>> www.isiahmeadows.com
>>
>> On Sun, Aug 26, 2018 at 12:20 PM Logan Smyth
>> wrote:
>> >
>> > Static class fields run their initializers and define the properties
>> > at declaration time, and class constructors have the parent class as
>> > the `[[Prototype]]`, so static field values are inherited. I think this
>> is adding to confusion though, because while that's absolutely true, that
>> is not applicable in the same way to non-static class fields, which is what
>> this original email is focused on. You could indeed also address this with
>> static properties in a proper ES6 environment as ``` class Base {
>> > static idAttribute = "id";
>> >
>> > constructor() {
>> >this.idAttribute = new.target.idAttribute;
>> > }
>> > }
>> > class Derived extends Base {
>> > static idAttribute = "_id";
>> >
>> > constructor() {
>> >super();
>> > }
>> > }
>> > ```
>> >
>> > On Sun, Aug 26, 2018 at 10:35 AM Isiah Meadows
>> wrote:
>> >>
>> >> Every object, including functions, have an internal prototype.
>> Functions normally have one set to `Function.prototype`, and objects
>> normally inherit from `Object.prototype` at least indirectly. But because
>> of how prototypes work, the only requirement for something to be used as a
>> prototype is that it must be an object. So you can do
>> `Object.create(someFunction)` and although you can't call it (it's not a
>> callable object), that object inherits all the properties and methods from
>> that function. `class` in JavaScript is just sugar over a common pattern
>> (really complex sugar requiring `new.target` to emulate, but still sugar),
>> not an entirely new concept, and it all builds off of prototypes.
>> Specifically, the instance prototyp
Re: constructor, super, and data members issue
I've been thinking about the problems around this some more. At first I
couldn't get past the dissenting arguments from issue #123, but I've since
come up with a solution that might work. What if:
* Make it illegal to define a class directly on a class field in a class
declaration.
* Move the assignment portion of a class field declaration into a getter on
the prototype such that the getter sets an own property on the instance if
it doesn't exist, then returns that value
What I mean is this:
```js
class Example {
//classField = class{}; //Error
otherField=[ "foo", "bar"];
}
class ES6Example {
//classField ignored for this example since it was an error.
get otherField() {
if ((this instanceof ES6Example) && !this.hasOwnProperty("otherField"))
this.otherField = [ "foo", "bar" ];
return this.otherField;
}
}
```
Done this way, any code expecting early assignment of a field being used as
though it were "abstract" will still work as expected.
On Thu, Aug 30, 2018 at 4:38 PM doodad-js Admin wrote:
> I'm late to the party, but I've found a solution for my non-loved
> framework : have another constructor called before "super", which fills a
> faked "this" and a faked "args" then replicated values to "this" after
> doing "super(...fakedArgs)".
>
>
> https://github.com/doodadjs/doodad-js/blob/v9.1.3/src/common/Bootstrap.js#L5320-L5330
>
> -Original Message-
> From: Isiah Meadows
> Sent: Sunday, August 26, 2018 3:29 PM
> To: Logan Smyth
> Cc: Ben Wiley ; es-discuss <
> es-discuss@mozilla.org>
> Subject: Re: constructor, super, and data members issue
>
> Yeah, I was more focused on the static class side of things, because I
> thought they were referring to that. Class instance fields are different,
> and so of course, those are never set on the prototype unless for whatever
> reason, the parent constructor returns `Object.getPrototypeOf(this)`
> instead of letting it default to the normal `this`.
>
> My bad, and you are correct.
>
> -
>
> Isiah Meadows
> cont...@isiahmeadows.com
> www.isiahmeadows.com
>
> On Sun, Aug 26, 2018 at 12:20 PM Logan Smyth
> wrote:
> >
> > Static class fields run their initializers and define the properties
> > at declaration time, and class constructors have the parent class as
> > the `[[Prototype]]`, so static field values are inherited. I think this
> is adding to confusion though, because while that's absolutely true, that
> is not applicable in the same way to non-static class fields, which is what
> this original email is focused on. You could indeed also address this with
> static properties in a proper ES6 environment as ``` class Base {
> > static idAttribute = "id";
> >
> > constructor() {
> >this.idAttribute = new.target.idAttribute;
> > }
> > }
> > class Derived extends Base {
> > static idAttribute = "_id";
> >
> > constructor() {
> >super();
> > }
> > }
> > ```
> >
> > On Sun, Aug 26, 2018 at 10:35 AM Isiah Meadows
> wrote:
> >>
> >> Every object, including functions, have an internal prototype.
> Functions normally have one set to `Function.prototype`, and objects
> normally inherit from `Object.prototype` at least indirectly. But because
> of how prototypes work, the only requirement for something to be used as a
> prototype is that it must be an object. So you can do
> `Object.create(someFunction)` and although you can't call it (it's not a
> callable object), that object inherits all the properties and methods from
> that function. `class` in JavaScript is just sugar over a common pattern
> (really complex sugar requiring `new.target` to emulate, but still sugar),
> not an entirely new concept, and it all builds off of prototypes.
> Specifically, the instance prototype inherits from the parent prototype,
> and the class constructor itself inherits from the parent constructor.
> That's why if you declare a static `call` method on a parent class, you can
> still access and use it in the subclass.
> >> On Sat, Aug 25, 2018 at 19:58 Ben Wiley
> wrote:
> >>>
> >>> How can they be prototypically inherited if they don't live on the
> prototype? I feel like I'm missing something.
> >>>
> >>> Le sam. 25 août 2018 19 h 53, Isiah Meadows
> a écrit :
> >>>>
> >>>> Class fields are prototypically inherited just like via `Object
> create`. This is more useful than you might think, and it's the main reason
> anyone actually cares about static fields beyond namespacing.
> >>>&
RE: constructor, super, and data members issue
I'm late to the party, but I've found a solution for my non-loved framework :
have another constructor called before "super", which fills a faked "this" and
a faked "args" then replicated values to "this" after doing
"super(...fakedArgs)".
https://github.com/doodadjs/doodad-js/blob/v9.1.3/src/common/Bootstrap.js#L5320-L5330
-Original Message-
From: Isiah Meadows
Sent: Sunday, August 26, 2018 3:29 PM
To: Logan Smyth
Cc: Ben Wiley ; es-discuss
Subject: Re: constructor, super, and data members issue
Yeah, I was more focused on the static class side of things, because I thought
they were referring to that. Class instance fields are different, and so of
course, those are never set on the prototype unless for whatever reason, the
parent constructor returns `Object.getPrototypeOf(this)` instead of letting it
default to the normal `this`.
My bad, and you are correct.
-
Isiah Meadows
cont...@isiahmeadows.com
www.isiahmeadows.com
On Sun, Aug 26, 2018 at 12:20 PM Logan Smyth wrote:
>
> Static class fields run their initializers and define the properties
> at declaration time, and class constructors have the parent class as
> the `[[Prototype]]`, so static field values are inherited. I think this is
> adding to confusion though, because while that's absolutely true, that is not
> applicable in the same way to non-static class fields, which is what this
> original email is focused on. You could indeed also address this with static
> properties in a proper ES6 environment as ``` class Base {
> static idAttribute = "id";
>
> constructor() {
>this.idAttribute = new.target.idAttribute;
> }
> }
> class Derived extends Base {
> static idAttribute = "_id";
>
> constructor() {
>super();
> }
> }
> ```
>
> On Sun, Aug 26, 2018 at 10:35 AM Isiah Meadows wrote:
>>
>> Every object, including functions, have an internal prototype. Functions
>> normally have one set to `Function.prototype`, and objects normally inherit
>> from `Object.prototype` at least indirectly. But because of how prototypes
>> work, the only requirement for something to be used as a prototype is that
>> it must be an object. So you can do `Object.create(someFunction)` and
>> although you can't call it (it's not a callable object), that object
>> inherits all the properties and methods from that function. `class` in
>> JavaScript is just sugar over a common pattern (really complex sugar
>> requiring `new.target` to emulate, but still sugar), not an entirely new
>> concept, and it all builds off of prototypes. Specifically, the instance
>> prototype inherits from the parent prototype, and the class constructor
>> itself inherits from the parent constructor. That's why if you declare a
>> static `call` method on a parent class, you can still access and use it in
>> the subclass.
>> On Sat, Aug 25, 2018 at 19:58 Ben Wiley wrote:
>>>
>>> How can they be prototypically inherited if they don't live on the
>>> prototype? I feel like I'm missing something.
>>>
>>> Le sam. 25 août 2018 19 h 53, Isiah Meadows a
>>> écrit :
>>>>
>>>> Class fields are prototypically inherited just like via `Object create`.
>>>> This is more useful than you might think, and it's the main reason anyone
>>>> actually cares about static fields beyond namespacing.
>>>> On Sat, Aug 25, 2018 at 14:36 Ben Wiley wrote:
>>>>>
>>>>> All this just reminds me of *my opinion* that class fields is a borrowed
>>>>> concept from statically typed languages that is misplaced in a
>>>>> dynamically typed languages like JavaScript.
>>>>>
>>>>> In C++ I use class fields to declare what properties will be allocated
>>>>> and instantiated when a new class member is constructed.
>>>>>
>>>>> In the ES proposal for class fields we mimic this type of behavior by
>>>>> instantiating properties on the object when it's constructed, but there's
>>>>> no runtime guarantee that this set of properties will remain the same.
>>>>>
>>>>> There's no reason not to put this in the constructor, and although
>>>>> putting class fields on the prototype is debatably not the best idea, it
>>>>> would be the only scenario where we get some kind of new helpful behavior
>>>>> out of it.
>>>>>
>>>>> Ben
>>>>>
>>>>> Le sam. 25 août 2018 14 h 25, Augusto Moura a
>>>>> écrit :
>>>
Re: constructor, super, and data members issue
Yeah, I was more focused on the static class side of things, because I
thought they were referring to that. Class instance fields are
different, and so of course, those are never set on the prototype
unless for whatever reason, the parent constructor returns
`Object.getPrototypeOf(this)` instead of letting it default to the
normal `this`.
My bad, and you are correct.
-
Isiah Meadows
cont...@isiahmeadows.com
www.isiahmeadows.com
On Sun, Aug 26, 2018 at 12:20 PM Logan Smyth wrote:
>
> Static class fields run their initializers and define the properties at
> declaration time, and class constructors have the parent class as the
> `[[Prototype]]`, so static field values are inherited. I think this is adding
> to confusion though, because while that's absolutely true, that is not
> applicable in the same way to non-static class fields, which is what this
> original email is focused on. You could indeed also address this with static
> properties in a proper ES6 environment as
> ```
> class Base {
> static idAttribute = "id";
>
> constructor() {
>this.idAttribute = new.target.idAttribute;
> }
> }
> class Derived extends Base {
> static idAttribute = "_id";
>
> constructor() {
>super();
> }
> }
> ```
>
> On Sun, Aug 26, 2018 at 10:35 AM Isiah Meadows wrote:
>>
>> Every object, including functions, have an internal prototype. Functions
>> normally have one set to `Function.prototype`, and objects normally inherit
>> from `Object.prototype` at least indirectly. But because of how prototypes
>> work, the only requirement for something to be used as a prototype is that
>> it must be an object. So you can do `Object.create(someFunction)` and
>> although you can't call it (it's not a callable object), that object
>> inherits all the properties and methods from that function. `class` in
>> JavaScript is just sugar over a common pattern (really complex sugar
>> requiring `new.target` to emulate, but still sugar), not an entirely new
>> concept, and it all builds off of prototypes. Specifically, the instance
>> prototype inherits from the parent prototype, and the class constructor
>> itself inherits from the parent constructor. That's why if you declare a
>> static `call` method on a parent class, you can still access and use it in
>> the subclass.
>> On Sat, Aug 25, 2018 at 19:58 Ben Wiley wrote:
>>>
>>> How can they be prototypically inherited if they don't live on the
>>> prototype? I feel like I'm missing something.
>>>
>>> Le sam. 25 août 2018 19 h 53, Isiah Meadows a
>>> écrit :
Class fields are prototypically inherited just like via `Object create`.
This is more useful than you might think, and it's the main reason anyone
actually cares about static fields beyond namespacing.
On Sat, Aug 25, 2018 at 14:36 Ben Wiley wrote:
>
> All this just reminds me of *my opinion* that class fields is a borrowed
> concept from statically typed languages that is misplaced in a
> dynamically typed languages like JavaScript.
>
> In C++ I use class fields to declare what properties will be allocated
> and instantiated when a new class member is constructed.
>
> In the ES proposal for class fields we mimic this type of behavior by
> instantiating properties on the object when it's constructed, but there's
> no runtime guarantee that this set of properties will remain the same.
>
> There's no reason not to put this in the constructor, and although
> putting class fields on the prototype is debatably not the best idea, it
> would be the only scenario where we get some kind of new helpful behavior
> out of it.
>
> Ben
>
> Le sam. 25 août 2018 14 h 25, Augusto Moura a
> écrit :
>>
>> 24-08-2018 19:29, Aaron Gray :
>>
>> >
>> > Yeah it does look like its badly "broken by design".
>> >
>>
>> Why this behaviour is broken? Every OOP language that I worked with
>> behaves de same way, and there's not many developers complaining about
>> it. If you want to use a property that might be overrided in a
>> subclasss you need to use a method and make the source of the data
>> more versatile (in Java and others similiar languages we have to
>> implement it using getter methods). Luckily Javascript doesn't need
>> getter and setters methods to make a property overridable because of
>> getter and setters descriptors, so we can workaround the first example
>> easily:
>>
>> ``` js
>> class Bar {
>> bar = 'in bar';
>>
>> constructor() {
>> console.log(this.bar)
>> }
>> }
>>
>> class Foo extends Bar {
>> _initiedSuper = false;
>> _bar = 'in foo';
>>
>> constructor() {
>> super();
>> this._initiedSuper = true;
>> }
>>
>> get bar() {
>> return this._bar;
>> }
>>
>> set bar(val) {
>>
Re: constructor, super, and data members issue
Static class fields run their initializers and define the properties at
declaration time, and class constructors have the parent class as the
`[[Prototype]]`, so static field values are inherited. I think this is
adding to confusion though, because while that's absolutely true, that is
not applicable in the same way to non-static class fields, which is what
this original email is focused on. You could indeed also address this with
static properties in a proper ES6 environment as
```
class Base {
static idAttribute = "id";
constructor() {
this.idAttribute = new.target.idAttribute;
}
}
class Derived extends Base {
static idAttribute = "_id";
constructor() {
super();
}
}
```
On Sun, Aug 26, 2018 at 10:35 AM Isiah Meadows
wrote:
> Every object, including functions, have an internal prototype. Functions
> normally have one set to `Function.prototype`, and objects normally inherit
> from `Object.prototype` at least indirectly. But because of how prototypes
> work, the only requirement for something to be used as a prototype is that
> it must be an object. So you can do `Object.create(someFunction)` and
> although you can't call it (it's not a callable object), that object
> inherits all the properties and methods from that function. `class` in
> JavaScript is just sugar over a common pattern (really complex sugar
> requiring `new.target` to emulate, but still sugar), not an entirely new
> concept, and it all builds off of prototypes. Specifically, the instance
> prototype inherits from the parent prototype, and the class constructor
> itself inherits from the parent constructor. That's why if you declare a
> static `call` method on a parent class, you can still access and use it in
> the subclass.
> On Sat, Aug 25, 2018 at 19:58 Ben Wiley wrote:
>
>> How can they be prototypically inherited if they don't live on the
>> prototype? I feel like I'm missing something.
>>
>> Le sam. 25 août 2018 19 h 53, Isiah Meadows a
>> écrit :
>>
>>> Class fields are prototypically inherited just like via `Object create`.
>>> This is more useful than you might think, and it's the main reason anyone
>>> actually cares about static fields beyond namespacing.
>>> On Sat, Aug 25, 2018 at 14:36 Ben Wiley
>>> wrote:
>>>
All this just reminds me of *my opinion* that class fields is a
borrowed concept from statically typed languages that is misplaced in a
dynamically typed languages like JavaScript.
In C++ I use class fields to declare what properties will be allocated
and instantiated when a new class member is constructed.
In the ES proposal for class fields we mimic this type of behavior by
instantiating properties on the object when it's constructed, but there's
no runtime guarantee that this set of properties will remain the same.
There's no reason not to put this in the constructor, and although
putting class fields on the prototype is debatably not the best idea, it
would be the only scenario where we get some kind of new helpful behavior
out of it.
Ben
Le sam. 25 août 2018 14 h 25, Augusto Moura
a écrit :
> 24-08-2018 19:29, Aaron Gray :
>
> >
> > Yeah it does look like its badly "broken by design".
> >
>
> Why this behaviour is broken? Every OOP language that I worked with
> behaves de same way, and there's not many developers complaining about
> it. If you want to use a property that might be overrided in a
> subclasss you need to use a method and make the source of the data
> more versatile (in Java and others similiar languages we have to
> implement it using getter methods). Luckily Javascript doesn't need
> getter and setters methods to make a property overridable because of
> getter and setters descriptors, so we can workaround the first example
> easily:
>
> ``` js
> class Bar {
> bar = 'in bar';
>
> constructor() {
> console.log(this.bar)
> }
> }
>
> class Foo extends Bar {
> _initiedSuper = false;
> _bar = 'in foo';
>
> constructor() {
> super();
> this._initiedSuper = true;
> }
>
> get bar() {
> return this._bar;
> }
>
> set bar(val) {
> if (this._initiedSuper) {
> this._bar = val;
> }
> }
> }
>
> new Foo(); // will log 'in foo'
> ```
>
> *I have to say the relaying that the super constructor will use the
> bar property and workarounding it **is a bad practice** and should be
> avoided at any costs. The contract with the super class constructor
> should rely only on the super call, these situations just reveal bad
> design choices in the super class. Logan Smyth example is the correct
> answer to this problem*
>
>
> 25-08-2018 01:28, Jordan Harband :
>
> >
> > Personally I think a design where
Re: constructor, super, and data members issue
Every object, including functions, have an internal prototype. Functions
normally have one set to `Function.prototype`, and objects normally inherit
from `Object.prototype` at least indirectly. But because of how prototypes
work, the only requirement for something to be used as a prototype is that
it must be an object. So you can do `Object.create(someFunction)` and
although you can't call it (it's not a callable object), that object
inherits all the properties and methods from that function. `class` in
JavaScript is just sugar over a common pattern (really complex sugar
requiring `new.target` to emulate, but still sugar), not an entirely new
concept, and it all builds off of prototypes. Specifically, the instance
prototype inherits from the parent prototype, and the class constructor
itself inherits from the parent constructor. That's why if you declare a
static `call` method on a parent class, you can still access and use it in
the subclass.
On Sat, Aug 25, 2018 at 19:58 Ben Wiley wrote:
> How can they be prototypically inherited if they don't live on the
> prototype? I feel like I'm missing something.
>
> Le sam. 25 août 2018 19 h 53, Isiah Meadows a
> écrit :
>
>> Class fields are prototypically inherited just like via `Object create`.
>> This is more useful than you might think, and it's the main reason anyone
>> actually cares about static fields beyond namespacing.
>> On Sat, Aug 25, 2018 at 14:36 Ben Wiley
>> wrote:
>>
>>> All this just reminds me of *my opinion* that class fields is a borrowed
>>> concept from statically typed languages that is misplaced in a dynamically
>>> typed languages like JavaScript.
>>>
>>> In C++ I use class fields to declare what properties will be allocated
>>> and instantiated when a new class member is constructed.
>>>
>>> In the ES proposal for class fields we mimic this type of behavior by
>>> instantiating properties on the object when it's constructed, but there's
>>> no runtime guarantee that this set of properties will remain the same.
>>>
>>> There's no reason not to put this in the constructor, and although
>>> putting class fields on the prototype is debatably not the best idea, it
>>> would be the only scenario where we get some kind of new helpful behavior
>>> out of it.
>>>
>>> Ben
>>>
>>> Le sam. 25 août 2018 14 h 25, Augusto Moura
>>> a écrit :
>>>
24-08-2018 19:29, Aaron Gray :
>
> Yeah it does look like its badly "broken by design".
>
Why this behaviour is broken? Every OOP language that I worked with
behaves de same way, and there's not many developers complaining about
it. If you want to use a property that might be overrided in a
subclasss you need to use a method and make the source of the data
more versatile (in Java and others similiar languages we have to
implement it using getter methods). Luckily Javascript doesn't need
getter and setters methods to make a property overridable because of
getter and setters descriptors, so we can workaround the first example
easily:
``` js
class Bar {
bar = 'in bar';
constructor() {
console.log(this.bar)
}
}
class Foo extends Bar {
_initiedSuper = false;
_bar = 'in foo';
constructor() {
super();
this._initiedSuper = true;
}
get bar() {
return this._bar;
}
set bar(val) {
if (this._initiedSuper) {
this._bar = val;
}
}
}
new Foo(); // will log 'in foo'
```
*I have to say the relaying that the super constructor will use the
bar property and workarounding it **is a bad practice** and should be
avoided at any costs. The contract with the super class constructor
should rely only on the super call, these situations just reveal bad
design choices in the super class. Logan Smyth example is the correct
answer to this problem*
25-08-2018 01:28, Jordan Harband :
>
> Personally I think a design where the superclass relies on any part
of the
> subclass is "broken by design"; but certainly there's ways you can
achieve
> that.
>
Of course is not broken. The super class has a contract with a
parametrized option, it can be used in subclasses or just in a
constructor call `new Base({ idAttribute: 'foo' })`, if it has a
default value for that is not a sub class concern. When refactoring
code adding defaults and "lifting" parameters are very common ~not
only on OOP~ and relying that the super class is using some property
in the constructor is the real "broken by design".
___
es-discuss mailing list
es-discuss@mozilla.org
https://mail.mozilla.org/listinfo/es-discuss
>>> ___
>>> es-discuss mailing list
>>>
Re: constructor, super, and data members issue
How can they be prototypically inherited if they don't live on the
prototype? I feel like I'm missing something.
Le sam. 25 août 2018 19 h 53, Isiah Meadows a
écrit :
> Class fields are prototypically inherited just like via `Object create`.
> This is more useful than you might think, and it's the main reason anyone
> actually cares about static fields beyond namespacing.
> On Sat, Aug 25, 2018 at 14:36 Ben Wiley wrote:
>
>> All this just reminds me of *my opinion* that class fields is a borrowed
>> concept from statically typed languages that is misplaced in a dynamically
>> typed languages like JavaScript.
>>
>> In C++ I use class fields to declare what properties will be allocated
>> and instantiated when a new class member is constructed.
>>
>> In the ES proposal for class fields we mimic this type of behavior by
>> instantiating properties on the object when it's constructed, but there's
>> no runtime guarantee that this set of properties will remain the same.
>>
>> There's no reason not to put this in the constructor, and although
>> putting class fields on the prototype is debatably not the best idea, it
>> would be the only scenario where we get some kind of new helpful behavior
>> out of it.
>>
>> Ben
>>
>> Le sam. 25 août 2018 14 h 25, Augusto Moura
>> a écrit :
>>
>>> 24-08-2018 19:29, Aaron Gray :
>>>
>>> >
>>> > Yeah it does look like its badly "broken by design".
>>> >
>>>
>>> Why this behaviour is broken? Every OOP language that I worked with
>>> behaves de same way, and there's not many developers complaining about
>>> it. If you want to use a property that might be overrided in a
>>> subclasss you need to use a method and make the source of the data
>>> more versatile (in Java and others similiar languages we have to
>>> implement it using getter methods). Luckily Javascript doesn't need
>>> getter and setters methods to make a property overridable because of
>>> getter and setters descriptors, so we can workaround the first example
>>> easily:
>>>
>>> ``` js
>>> class Bar {
>>> bar = 'in bar';
>>>
>>> constructor() {
>>> console.log(this.bar)
>>> }
>>> }
>>>
>>> class Foo extends Bar {
>>> _initiedSuper = false;
>>> _bar = 'in foo';
>>>
>>> constructor() {
>>> super();
>>> this._initiedSuper = true;
>>> }
>>>
>>> get bar() {
>>> return this._bar;
>>> }
>>>
>>> set bar(val) {
>>> if (this._initiedSuper) {
>>> this._bar = val;
>>> }
>>> }
>>> }
>>>
>>> new Foo(); // will log 'in foo'
>>> ```
>>>
>>> *I have to say the relaying that the super constructor will use the
>>> bar property and workarounding it **is a bad practice** and should be
>>> avoided at any costs. The contract with the super class constructor
>>> should rely only on the super call, these situations just reveal bad
>>> design choices in the super class. Logan Smyth example is the correct
>>> answer to this problem*
>>>
>>>
>>> 25-08-2018 01:28, Jordan Harband :
>>>
>>> >
>>> > Personally I think a design where the superclass relies on any part of
>>> the
>>> > subclass is "broken by design"; but certainly there's ways you can
>>> achieve
>>> > that.
>>> >
>>>
>>> Of course is not broken. The super class has a contract with a
>>> parametrized option, it can be used in subclasses or just in a
>>> constructor call `new Base({ idAttribute: 'foo' })`, if it has a
>>> default value for that is not a sub class concern. When refactoring
>>> code adding defaults and "lifting" parameters are very common ~not
>>> only on OOP~ and relying that the super class is using some property
>>> in the constructor is the real "broken by design".
>>> ___
>>> es-discuss mailing list
>>> es-discuss@mozilla.org
>>> https://mail.mozilla.org/listinfo/es-discuss
>>>
>> ___
>> es-discuss mailing list
>> es-discuss@mozilla.org
>> https://mail.mozilla.org/listinfo/es-discuss
>>
>
___
es-discuss mailing list
es-discuss@mozilla.org
https://mail.mozilla.org/listinfo/es-discuss
Re: constructor, super, and data members issue
Class fields are prototypically inherited just like via `Object create`.
This is more useful than you might think, and it's the main reason anyone
actually cares about static fields beyond namespacing.
On Sat, Aug 25, 2018 at 14:36 Ben Wiley wrote:
> All this just reminds me of *my opinion* that class fields is a borrowed
> concept from statically typed languages that is misplaced in a dynamically
> typed languages like JavaScript.
>
> In C++ I use class fields to declare what properties will be allocated and
> instantiated when a new class member is constructed.
>
> In the ES proposal for class fields we mimic this type of behavior by
> instantiating properties on the object when it's constructed, but there's
> no runtime guarantee that this set of properties will remain the same.
>
> There's no reason not to put this in the constructor, and although putting
> class fields on the prototype is debatably not the best idea, it would be
> the only scenario where we get some kind of new helpful behavior out of it.
>
> Ben
>
> Le sam. 25 août 2018 14 h 25, Augusto Moura a
> écrit :
>
>> 24-08-2018 19:29, Aaron Gray :
>>
>> >
>> > Yeah it does look like its badly "broken by design".
>> >
>>
>> Why this behaviour is broken? Every OOP language that I worked with
>> behaves de same way, and there's not many developers complaining about
>> it. If you want to use a property that might be overrided in a
>> subclasss you need to use a method and make the source of the data
>> more versatile (in Java and others similiar languages we have to
>> implement it using getter methods). Luckily Javascript doesn't need
>> getter and setters methods to make a property overridable because of
>> getter and setters descriptors, so we can workaround the first example
>> easily:
>>
>> ``` js
>> class Bar {
>> bar = 'in bar';
>>
>> constructor() {
>> console.log(this.bar)
>> }
>> }
>>
>> class Foo extends Bar {
>> _initiedSuper = false;
>> _bar = 'in foo';
>>
>> constructor() {
>> super();
>> this._initiedSuper = true;
>> }
>>
>> get bar() {
>> return this._bar;
>> }
>>
>> set bar(val) {
>> if (this._initiedSuper) {
>> this._bar = val;
>> }
>> }
>> }
>>
>> new Foo(); // will log 'in foo'
>> ```
>>
>> *I have to say the relaying that the super constructor will use the
>> bar property and workarounding it **is a bad practice** and should be
>> avoided at any costs. The contract with the super class constructor
>> should rely only on the super call, these situations just reveal bad
>> design choices in the super class. Logan Smyth example is the correct
>> answer to this problem*
>>
>>
>> 25-08-2018 01:28, Jordan Harband :
>>
>> >
>> > Personally I think a design where the superclass relies on any part of
>> the
>> > subclass is "broken by design"; but certainly there's ways you can
>> achieve
>> > that.
>> >
>>
>> Of course is not broken. The super class has a contract with a
>> parametrized option, it can be used in subclasses or just in a
>> constructor call `new Base({ idAttribute: 'foo' })`, if it has a
>> default value for that is not a sub class concern. When refactoring
>> code adding defaults and "lifting" parameters are very common ~not
>> only on OOP~ and relying that the super class is using some property
>> in the constructor is the real "broken by design".
>> ___
>> es-discuss mailing list
>> es-discuss@mozilla.org
>> https://mail.mozilla.org/listinfo/es-discuss
>>
> ___
> es-discuss mailing list
> es-discuss@mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
>
___
es-discuss mailing list
es-discuss@mozilla.org
https://mail.mozilla.org/listinfo/es-discuss
Re: constructor, super, and data members issue
All this just reminds me of *my opinion* that class fields is a borrowed
concept from statically typed languages that is misplaced in a dynamically
typed languages like JavaScript.
In C++ I use class fields to declare what properties will be allocated and
instantiated when a new class member is constructed.
In the ES proposal for class fields we mimic this type of behavior by
instantiating properties on the object when it's constructed, but there's
no runtime guarantee that this set of properties will remain the same.
There's no reason not to put this in the constructor, and although putting
class fields on the prototype is debatably not the best idea, it would be
the only scenario where we get some kind of new helpful behavior out of it.
Ben
Le sam. 25 août 2018 14 h 25, Augusto Moura a
écrit :
> 24-08-2018 19:29, Aaron Gray :
>
> >
> > Yeah it does look like its badly "broken by design".
> >
>
> Why this behaviour is broken? Every OOP language that I worked with
> behaves de same way, and there's not many developers complaining about
> it. If you want to use a property that might be overrided in a
> subclasss you need to use a method and make the source of the data
> more versatile (in Java and others similiar languages we have to
> implement it using getter methods). Luckily Javascript doesn't need
> getter and setters methods to make a property overridable because of
> getter and setters descriptors, so we can workaround the first example
> easily:
>
> ``` js
> class Bar {
> bar = 'in bar';
>
> constructor() {
> console.log(this.bar)
> }
> }
>
> class Foo extends Bar {
> _initiedSuper = false;
> _bar = 'in foo';
>
> constructor() {
> super();
> this._initiedSuper = true;
> }
>
> get bar() {
> return this._bar;
> }
>
> set bar(val) {
> if (this._initiedSuper) {
> this._bar = val;
> }
> }
> }
>
> new Foo(); // will log 'in foo'
> ```
>
> *I have to say the relaying that the super constructor will use the
> bar property and workarounding it **is a bad practice** and should be
> avoided at any costs. The contract with the super class constructor
> should rely only on the super call, these situations just reveal bad
> design choices in the super class. Logan Smyth example is the correct
> answer to this problem*
>
>
> 25-08-2018 01:28, Jordan Harband :
>
> >
> > Personally I think a design where the superclass relies on any part of
> the
> > subclass is "broken by design"; but certainly there's ways you can
> achieve
> > that.
> >
>
> Of course is not broken. The super class has a contract with a
> parametrized option, it can be used in subclasses or just in a
> constructor call `new Base({ idAttribute: 'foo' })`, if it has a
> default value for that is not a sub class concern. When refactoring
> code adding defaults and "lifting" parameters are very common ~not
> only on OOP~ and relying that the super class is using some property
> in the constructor is the real "broken by design".
> ___
> es-discuss mailing list
> es-discuss@mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
>
___
es-discuss mailing list
es-discuss@mozilla.org
https://mail.mozilla.org/listinfo/es-discuss
Re: constructor, super, and data members issue
24-08-2018 19:29, Aaron Gray :
>
> Yeah it does look like its badly "broken by design".
>
Why this behaviour is broken? Every OOP language that I worked with
behaves de same way, and there's not many developers complaining about
it. If you want to use a property that might be overrided in a
subclasss you need to use a method and make the source of the data
more versatile (in Java and others similiar languages we have to
implement it using getter methods). Luckily Javascript doesn't need
getter and setters methods to make a property overridable because of
getter and setters descriptors, so we can workaround the first example
easily:
``` js
class Bar {
bar = 'in bar';
constructor() {
console.log(this.bar)
}
}
class Foo extends Bar {
_initiedSuper = false;
_bar = 'in foo';
constructor() {
super();
this._initiedSuper = true;
}
get bar() {
return this._bar;
}
set bar(val) {
if (this._initiedSuper) {
this._bar = val;
}
}
}
new Foo(); // will log 'in foo'
```
*I have to say the relaying that the super constructor will use the
bar property and workarounding it **is a bad practice** and should be
avoided at any costs. The contract with the super class constructor
should rely only on the super call, these situations just reveal bad
design choices in the super class. Logan Smyth example is the correct
answer to this problem*
25-08-2018 01:28, Jordan Harband :
>
> Personally I think a design where the superclass relies on any part of the
> subclass is "broken by design"; but certainly there's ways you can achieve
> that.
>
Of course is not broken. The super class has a contract with a
parametrized option, it can be used in subclasses or just in a
constructor call `new Base({ idAttribute: 'foo' })`, if it has a
default value for that is not a sub class concern. When refactoring
code adding defaults and "lifting" parameters are very common ~not
only on OOP~ and relying that the super class is using some property
in the constructor is the real "broken by design".
___
es-discuss mailing list
es-discuss@mozilla.org
https://mail.mozilla.org/listinfo/es-discuss
Re: constructor, super, and data members issue
Base cases that take dependencies upon information potentially supplied by
subclass have to be intentionally design to make that work. And the chosen
design should be document as part of its subclassing contract. For the example
shown there is there is a long known pattern that can be used:
class Base {
constructor() {
.. idAttribute ..
}
idAttribute = this.__idInitializer(); //initial id value may be
supplied by a subclass
__idInitialier() {
// override this method if you want your subclass to provide an
alternative initial idAttribute value
// the subclass override method should not be dependent upon
subclass fields.
return ‘id’;
’}
}
class Derived extends Base {
constructor() {
super();
}
__idInitializer() {return ‘_id’}
}
___
es-discuss mailing list
es-discuss@mozilla.org
https://mail.mozilla.org/listinfo/es-discuss
Re: constructor, super, and data members issue
On Sat, 25 Aug 2018 at 00:35, Logan Smyth wrote:
> Generally if something is required during construction, it would be best
> to pass it down as part of the constructor options. For example, you could
> do
> ```
> class Base {
> constructor({ idAttribute = "id"}) {
> this.idAttribute = idAttribute;
> }
> }
>
> class Derived extends Base {
> constructor() {
> super({
> idAttribute: '_id'
> });
> }
> }
> ```
>
I had derived a simular solution.
> I don't think class fields would be a good way to conceptually do this
> kind of thing.
>
It was neat for what I wanted to do.
>
>
> On Fri, Aug 24, 2018 at 2:56 PM, Aaron Gray
> wrote:
>
>> Yeah it does look like its badly "broken by design".
>>
>> On Fri, 24 Aug 2018 at 22:13, Jordan Harband wrote:
>>
>>> I'm afraid that still wouldn't solve the problem; the superclass's code
>>> is all 100% completed before the subclass has `this` available.
>>>
>>> On Fri, Aug 24, 2018 at 1:52 PM, Ranando King wrote:
>>>
Aaron, congratulations! You just tripped over a new reason for me to
revive issue #123. The only way to get that to work is to have the default
values on the prototype. The problem comes because `this` doesn't even have
a value until the last call to `super()` returns. If a `class` doesn't have
a base `class` it essentially has Object as a base `class` and `super` is
implicitly called. So unless the default public field values are on the
prototype, there's literally no way to have them initialized before the
base classes are initialized.
On Fri, Aug 24, 2018 at 3:15 PM Aaron Gray
wrote:
> I am having an issue with order semantics regarding
> https://github.com/tc39/proposal-class-fields with derived classes
> defining or overriding data member values that are used in the base class
> constructor for initialization of properties of the class.
>
> This means the Super Class / Base Class'es constructor does not yet
> have access to the default field values of the derived class it is
> initiating.
>
> class Base {
> constructor() {
>
> .. idAttribute ..
>
> }
> idAttribute = 'id';
> }
>class Derived extends Base {
> constructor() {
> super();
>
> }
> idAttribute = '_id';
>}
>
> All would mean having a separate initialize() function, but even this
> solution is flawed when there is a third level in the hierarchy. And as
> super() is required it means there seems to be no way round this issue.
> The
> only way I can see is some form of override keyword ?
>
>
> Has anyone got any solutions to this issue or work arounds ?
> --
> Aaron Gray
>
> Independent Open Source Software Engineer, Computer Language
> Researcher, Information Theorist, and amateur computer scientist.
> ___
> es-discuss mailing list
> es-discuss@mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
>
___
es-discuss mailing list
es-discuss@mozilla.org
https://mail.mozilla.org/listinfo/es-discuss
>>>
>>
>> --
>> Aaron Gray
>>
>> Independent Open Source Software Engineer, Computer Language Researcher,
>> Information Theorist, and amateur computer scientist.
>>
>> ___
>> es-discuss mailing list
>> es-discuss@mozilla.org
>> https://mail.mozilla.org/listinfo/es-discuss
>>
>>
>
--
Aaron Gray
Independent Open Source Software Engineer, Computer Language Researcher,
Information Theorist, and amateur computer scientist.
___
es-discuss mailing list
es-discuss@mozilla.org
https://mail.mozilla.org/listinfo/es-discuss
Re: constructor, super, and data members issue
Personally I think a design where the superclass relies on any part of the
subclass is "broken by design"; but certainly there's ways you can achieve
that.
On Fri, Aug 24, 2018 at 4:34 PM, Logan Smyth wrote:
> Generally if something is required during construction, it would be best
> to pass it down as part of the constructor options. For example, you could
> do
> ```
> class Base {
> constructor({ idAttribute = "id"}) {
> this.idAttribute = idAttribute;
> }
> }
>
> class Derived extends Base {
> constructor() {
> super({
> idAttribute: '_id'
> });
> }
> }
> ```
>
> I don't think class fields would be a good way to conceptually do this
> kind of thing.
>
>
> On Fri, Aug 24, 2018 at 2:56 PM, Aaron Gray
> wrote:
>
>> Yeah it does look like its badly "broken by design".
>>
>> On Fri, 24 Aug 2018 at 22:13, Jordan Harband wrote:
>>
>>> I'm afraid that still wouldn't solve the problem; the superclass's code
>>> is all 100% completed before the subclass has `this` available.
>>>
>>> On Fri, Aug 24, 2018 at 1:52 PM, Ranando King wrote:
>>>
Aaron, congratulations! You just tripped over a new reason for me to
revive issue #123. The only way to get that to work is to have the default
values on the prototype. The problem comes because `this` doesn't even have
a value until the last call to `super()` returns. If a `class` doesn't have
a base `class` it essentially has Object as a base `class` and `super` is
implicitly called. So unless the default public field values are on the
prototype, there's literally no way to have them initialized before the
base classes are initialized.
On Fri, Aug 24, 2018 at 3:15 PM Aaron Gray
wrote:
> I am having an issue with order semantics regarding
> https://github.com/tc39/proposal-class-fields with derived classes
> defining or overriding data member values that are used in the base class
> constructor for initialization of properties of the class.
>
> This means the Super Class / Base Class'es constructor does not yet
> have access to the default field values of the derived class it is
> initiating.
>
> class Base {
> constructor() {
>
> .. idAttribute ..
>
> }
> idAttribute = 'id';
> }
>class Derived extends Base {
> constructor() {
> super();
>
> }
> idAttribute = '_id';
>}
>
> All would mean having a separate initialize() function, but even this
> solution is flawed when there is a third level in the hierarchy. And as
> super() is required it means there seems to be no way round this issue.
> The
> only way I can see is some form of override keyword ?
>
>
> Has anyone got any solutions to this issue or work arounds ?
> --
> Aaron Gray
>
> Independent Open Source Software Engineer, Computer Language
> Researcher, Information Theorist, and amateur computer scientist.
> ___
> es-discuss mailing list
> es-discuss@mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
>
___
es-discuss mailing list
es-discuss@mozilla.org
https://mail.mozilla.org/listinfo/es-discuss
>>>
>>
>> --
>> Aaron Gray
>>
>> Independent Open Source Software Engineer, Computer Language Researcher,
>> Information Theorist, and amateur computer scientist.
>>
>> ___
>> es-discuss mailing list
>> es-discuss@mozilla.org
>> https://mail.mozilla.org/listinfo/es-discuss
>>
>>
>
___
es-discuss mailing list
es-discuss@mozilla.org
https://mail.mozilla.org/listinfo/es-discuss
Re: constructor, super, and data members issue
Generally if something is required during construction, it would be best to
pass it down as part of the constructor options. For example, you could do
```
class Base {
constructor({ idAttribute = "id"}) {
this.idAttribute = idAttribute;
}
}
class Derived extends Base {
constructor() {
super({
idAttribute: '_id'
});
}
}
```
I don't think class fields would be a good way to conceptually do this kind
of thing.
On Fri, Aug 24, 2018 at 2:56 PM, Aaron Gray
wrote:
> Yeah it does look like its badly "broken by design".
>
> On Fri, 24 Aug 2018 at 22:13, Jordan Harband wrote:
>
>> I'm afraid that still wouldn't solve the problem; the superclass's code
>> is all 100% completed before the subclass has `this` available.
>>
>> On Fri, Aug 24, 2018 at 1:52 PM, Ranando King wrote:
>>
>>> Aaron, congratulations! You just tripped over a new reason for me to
>>> revive issue #123. The only way to get that to work is to have the default
>>> values on the prototype. The problem comes because `this` doesn't even have
>>> a value until the last call to `super()` returns. If a `class` doesn't have
>>> a base `class` it essentially has Object as a base `class` and `super` is
>>> implicitly called. So unless the default public field values are on the
>>> prototype, there's literally no way to have them initialized before the
>>> base classes are initialized.
>>>
>>> On Fri, Aug 24, 2018 at 3:15 PM Aaron Gray
>>> wrote:
>>>
I am having an issue with order semantics regarding https://github.com/
tc39/proposal-class-fields with derived classes defining or overriding
data member values that are used in the base class constructor for
initialization of properties of the class.
This means the Super Class / Base Class'es constructor does not yet
have access to the default field values of the derived class it is
initiating.
class Base {
constructor() {
.. idAttribute ..
}
idAttribute = 'id';
}
class Derived extends Base {
constructor() {
super();
}
idAttribute = '_id';
}
All would mean having a separate initialize() function, but even this
solution is flawed when there is a third level in the hierarchy. And as
super() is required it means there seems to be no way round this issue. The
only way I can see is some form of override keyword ?
Has anyone got any solutions to this issue or work arounds ?
--
Aaron Gray
Independent Open Source Software Engineer, Computer Language
Researcher, Information Theorist, and amateur computer scientist.
___
es-discuss mailing list
es-discuss@mozilla.org
https://mail.mozilla.org/listinfo/es-discuss
>>>
>>> ___
>>> es-discuss mailing list
>>> es-discuss@mozilla.org
>>> https://mail.mozilla.org/listinfo/es-discuss
>>>
>>>
>>
>
> --
> Aaron Gray
>
> Independent Open Source Software Engineer, Computer Language Researcher,
> Information Theorist, and amateur computer scientist.
>
> ___
> es-discuss mailing list
> es-discuss@mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
>
>
___
es-discuss mailing list
es-discuss@mozilla.org
https://mail.mozilla.org/listinfo/es-discuss
Re: constructor, super, and data members issue
Yeah it does look like its badly "broken by design".
On Fri, 24 Aug 2018 at 22:13, Jordan Harband wrote:
> I'm afraid that still wouldn't solve the problem; the superclass's code is
> all 100% completed before the subclass has `this` available.
>
> On Fri, Aug 24, 2018 at 1:52 PM, Ranando King wrote:
>
>> Aaron, congratulations! You just tripped over a new reason for me to
>> revive issue #123. The only way to get that to work is to have the default
>> values on the prototype. The problem comes because `this` doesn't even have
>> a value until the last call to `super()` returns. If a `class` doesn't have
>> a base `class` it essentially has Object as a base `class` and `super` is
>> implicitly called. So unless the default public field values are on the
>> prototype, there's literally no way to have them initialized before the
>> base classes are initialized.
>>
>> On Fri, Aug 24, 2018 at 3:15 PM Aaron Gray
>> wrote:
>>
>>> I am having an issue with order semantics regarding
>>> https://github.com/tc39/proposal-class-fields with derived classes
>>> defining or overriding data member values that are used in the base class
>>> constructor for initialization of properties of the class.
>>>
>>> This means the Super Class / Base Class'es constructor does not yet have
>>> access to the default field values of the derived class it is initiating.
>>>
>>> class Base {
>>> constructor() {
>>>
>>> .. idAttribute ..
>>>
>>> }
>>> idAttribute = 'id';
>>> }
>>>class Derived extends Base {
>>> constructor() {
>>> super();
>>>
>>> }
>>> idAttribute = '_id';
>>>}
>>>
>>> All would mean having a separate initialize() function, but even this
>>> solution is flawed when there is a third level in the hierarchy. And as
>>> super() is required it means there seems to be no way round this issue. The
>>> only way I can see is some form of override keyword ?
>>>
>>>
>>> Has anyone got any solutions to this issue or work arounds ?
>>> --
>>> Aaron Gray
>>>
>>> Independent Open Source Software Engineer, Computer Language Researcher,
>>> Information Theorist, and amateur computer scientist.
>>> ___
>>> es-discuss mailing list
>>> es-discuss@mozilla.org
>>> https://mail.mozilla.org/listinfo/es-discuss
>>>
>>
>> ___
>> es-discuss mailing list
>> es-discuss@mozilla.org
>> https://mail.mozilla.org/listinfo/es-discuss
>>
>>
>
--
Aaron Gray
Independent Open Source Software Engineer, Computer Language Researcher,
Information Theorist, and amateur computer scientist.
___
es-discuss mailing list
es-discuss@mozilla.org
https://mail.mozilla.org/listinfo/es-discuss
Re: constructor, super, and data members issue
I'm afraid that still wouldn't solve the problem; the superclass's code is
all 100% completed before the subclass has `this` available.
On Fri, Aug 24, 2018 at 1:52 PM, Ranando King wrote:
> Aaron, congratulations! You just tripped over a new reason for me to
> revive issue #123. The only way to get that to work is to have the default
> values on the prototype. The problem comes because `this` doesn't even have
> a value until the last call to `super()` returns. If a `class` doesn't have
> a base `class` it essentially has Object as a base `class` and `super` is
> implicitly called. So unless the default public field values are on the
> prototype, there's literally no way to have them initialized before the
> base classes are initialized.
>
> On Fri, Aug 24, 2018 at 3:15 PM Aaron Gray
> wrote:
>
>> I am having an issue with order semantics regarding https://github.com/
>> tc39/proposal-class-fields with derived classes defining or overriding
>> data member values that are used in the base class constructor for
>> initialization of properties of the class.
>>
>> This means the Super Class / Base Class'es constructor does not yet have
>> access to the default field values of the derived class it is initiating.
>>
>> class Base {
>> constructor() {
>>
>> .. idAttribute ..
>>
>> }
>> idAttribute = 'id';
>> }
>>class Derived extends Base {
>> constructor() {
>> super();
>>
>> }
>> idAttribute = '_id';
>>}
>>
>> All would mean having a separate initialize() function, but even this
>> solution is flawed when there is a third level in the hierarchy. And as
>> super() is required it means there seems to be no way round this issue. The
>> only way I can see is some form of override keyword ?
>>
>>
>> Has anyone got any solutions to this issue or work arounds ?
>> --
>> Aaron Gray
>>
>> Independent Open Source Software Engineer, Computer Language Researcher,
>> Information Theorist, and amateur computer scientist.
>> ___
>> es-discuss mailing list
>> es-discuss@mozilla.org
>> https://mail.mozilla.org/listinfo/es-discuss
>>
>
> ___
> es-discuss mailing list
> es-discuss@mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
>
>
___
es-discuss mailing list
es-discuss@mozilla.org
https://mail.mozilla.org/listinfo/es-discuss
Re: constructor, super, and data members issue
Aaron, congratulations! You just tripped over a new reason for me to revive
issue #123. The only way to get that to work is to have the default values
on the prototype. The problem comes because `this` doesn't even have a
value until the last call to `super()` returns. If a `class` doesn't have a
base `class` it essentially has Object as a base `class` and `super` is
implicitly called. So unless the default public field values are on the
prototype, there's literally no way to have them initialized before the
base classes are initialized.
On Fri, Aug 24, 2018 at 3:15 PM Aaron Gray
wrote:
> I am having an issue with order semantics regarding
> https://github.com/tc39/proposal-class-fields with derived classes
> defining or overriding data member values that are used in the base class
> constructor for initialization of properties of the class.
>
> This means the Super Class / Base Class'es constructor does not yet have
> access to the default field values of the derived class it is initiating.
>
> class Base {
> constructor() {
>
> .. idAttribute ..
>
> }
> idAttribute = 'id';
> }
>class Derived extends Base {
> constructor() {
> super();
>
> }
> idAttribute = '_id';
>}
>
> All would mean having a separate initialize() function, but even this
> solution is flawed when there is a third level in the hierarchy. And as
> super() is required it means there seems to be no way round this issue. The
> only way I can see is some form of override keyword ?
>
>
> Has anyone got any solutions to this issue or work arounds ?
> --
> Aaron Gray
>
> Independent Open Source Software Engineer, Computer Language Researcher,
> Information Theorist, and amateur computer scientist.
> ___
> es-discuss mailing list
> es-discuss@mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
>
___
es-discuss mailing list
es-discuss@mozilla.org
https://mail.mozilla.org/listinfo/es-discuss
constructor, super, and data members issue
I am having an issue with order semantics regarding
https://github.com/tc39/proposal-class-fields with derived classes defining
or overriding data member values that are used in the base class
constructor for initialization of properties of the class.
This means the Super Class / Base Class'es constructor does not yet have
access to the default field values of the derived class it is initiating.
class Base {
constructor() {
.. idAttribute ..
}
idAttribute = 'id';
}
class Derived extends Base {
constructor() {
super();
}
idAttribute = '_id';
}
All would mean having a separate initialize() function, but even this
solution is flawed when there is a third level in the hierarchy. And as
super() is required it means there seems to be no way round this issue. The
only way I can see is some form of override keyword ?
Has anyone got any solutions to this issue or work arounds ?
--
Aaron Gray
Independent Open Source Software Engineer, Computer Language Researcher,
Information Theorist, and amateur computer scientist.
___
es-discuss mailing list
es-discuss@mozilla.org
https://mail.mozilla.org/listinfo/es-discuss
