RE: [flexcoders] Array reference vs values
I think this has been explained several times already in this thread,
but you don't seem to have understood so I'll try explaining with some
ASCII art. Before assigning timeArr[2] = null you have
person.lunch >
^
|
timeArr[2] ---
After assigning timeArr[2] = null you have
person.lunch >
timeArr[2] -->
You are not nulling the Date instance. (I don't even know what that
would mean.) You are nulling the 2nd element in the timeArr Array which
referred to the Date instance.
Basically, AS reference are like C++ pointers, not like C++ references.
If you are trying to represent a sequence of times, don't use five vars
in Person named wakeup, breakfast, lunch, dinner, and bedtime. Use a
single Array with five elements
var times:Array /* of Date /;
and use the constants
static const WAKEUP:int = 0;
static const BREAKFAST:int = 1;
static const LUNCH:int = 2;
static const DINNER:int = 3;
static const BEDTIME:int = 4;
to access them as times[LUNCH], etc.
Gordon Smith
Adobe Flex SDK Team
From: flexcoders@yahoogroups.com [mailto:[EMAIL PROTECTED] On
Behalf Of Darren Houle
Sent: Wednesday, July 16, 2008 6:56 PM
To: flexcoders@yahoogroups.com
Subject: RE: [flexcoders] Array reference vs values
Josh
Yes, what you're describing is exactly what I described and is, in fact,
what it happening... but to say I don't ever need to do this? Well...
yes... I need to do this... and it has nothing to do with the garbage
collector.
Here, let me explain in another way
I have a custom object... lets say it's a Person object. It has various
properties, but several are Date types. These are all consecutive, like
a workflow, and I want to be able to address them in order via an
array... like this...
var person : Person = new Person();
person.wakeup = new Date();
person.breakfast = new Date();
person.lunch = new Date();
person.dinner = null;
person.bedtime = null;
var timeArr : Array = new Array();
timeArr[0] = person.wakeup;
timeArr[1] = person.breakfast;
timeArr[2] = person.lunch;
timeArr[3] = person.dinner;
timeArr[4] = person.bedtime;
Then some other code figures out where we are in the flow of the day's
events...
var status : int;
if (some criteria)
{ event = 2; }
But I determine lunch hasn't actually happened yet, so it shouldn't have
a Date yet. I need to blank out this value that was previously set in
the Person object...
if (some criteria)
{ timeArr[event] = null; }
But since these references don't seem to propogate backwards, nulling
one of the array elements doesn't affect the original property. That's
the *whole purpose* of reference vs value... a reference is a pointer to
memory space... so if I null that memory space it should affect all the
vars pointing to that memory space.
Does that make more sense?
Darren
To: flexcoders@yahoogroups.com
From: [EMAIL PROTECTED]
Date: Thu, 17 Jul 2008 11:30:29 +1000
Subject: Re: [flexcoders] Array reference vs values
When you do this:
var date:Date = new Date();
You're creating an instance of Date and a reference to it named "date".
When you do this:
var ref:Date = arr[0] as Date;
You're creating another reference to the same instance, this time your
reference is named "ref". So when you set ref = null, you're making
"ref" point to nothing. "date" and "arr[0]" remain unchanged. You don't
need to, nor can you remove the date instance created above. That's the
job of the garbage collector.
-Josh
On Thu, Jul 17, 2008 at 11:25 AM, Darren Houle <[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]> > wrote:
This might be a basic AS question, but I encountered it building a
Flex app, so...
I create a Date
var date:Date = new Date();
I create an Array
var arr:Array = new Array();
I set the first element of the array equal to the date
arr[0] = date;
I create another date variable that refers to the first array element
var ref:Date = arr[0] as Date;
if I trace("date="+date+", arr[0]="+arr[0]+", ref="+ref) I get
date=Wed Jul 16 21:04:45 GMT-0400 2008, arr[0]=Wed Jul 16 21:04:45
GMT-0400 2008, ref=Wed Jul 16 21:04:45 GMT-0400 2008
Now I null out the ref variable
ref=null;
Since AS uses references instead of values I would expect to null out
the original date, but no...
If I trace("date="+date+", arr[0]="+arr[0]+", ref="+ref) I now get
date=Wed Jul 16 21:04:45 GMT-0400 2008, arr[0]=Wed Jul 16 21:04:45
GMT-0400 2008, ref=null
I thought everything was a reference in AS? Shouldn't nulling ref
also null arr[0] which would null out date?
Ultim
RE: [flexcoders] Array reference vs values
If you're trying to say that Array is passed by value, that's incorrect.
Array is passed by reference, just like Object.
Gordon Smith
Adobe Flex SDK Team
From: flexcoders@yahoogroups.com [mailto:[EMAIL PROTECTED] On
Behalf Of Sherif Abdou
Sent: Wednesday, July 16, 2008 7:03 PM
To: flexcoders@yahoogroups.com
Subject: Re: [flexcoders] Array reference vs values
I think you may be able to do what you are doing by using the ByteArray
class but I would wait for someone that knows more than me. The only
things that get passed by reference is any class that inherits from an
Object and Array is a native Flash player class in C++.
- Original Message
From: Sherif Abdou <[EMAIL PROTECTED]>
To: flexcoders@yahoogroups.com
Sent: Wednesday, July 16, 2008 8:59:54 PM
Subject: Re: [flexcoders] Array reference vs values
If i remember correctly since I am mixing too much C++,ActionScript,
Coldfusion and learning them all the same time. Any of the primitive
stuff in Actionscript get passed only by value and not by reference so
you can't do what you are doing.
- Original Message
From: Darren Houle <[EMAIL PROTECTED] com>
To: [EMAIL PROTECTED] ups.com
Sent: Wednesday, July 16, 2008 8:55:33 PM
Subject: RE: [flexcoders] Array reference vs values
Josh
Yes, what you're describing is exactly what I described and is, in fact,
what it happening... but to say I don't ever need to do this? Well...
yes... I need to do this... and it has nothing to do with the garbage
collector.
Here, let me explain in another way
I have a custom object... lets say it's a Person object. It has various
properties, but several are Date types. These are all consecutive, like
a workflow, and I want to be able to address them in order via an
array... like this...
var person : Person = new Person();
person.wakeup = new Date();
person.breakfast = new Date();
person.lunch = new Date();
person.dinner = null;
person.bedtime = null;
var timeArr : Array = new Array();
timeArr[0] = person.wakeup;
timeArr[1] = person.breakfast;
timeArr[2] = person.lunch;
timeArr[3] = person.dinner;
timeArr[4] = person.bedtime;
Then some other code figures out where we are in the flow of the day's
events...
var status : int;
if (some criteria)
{ event = 2; }
But I determine lunch hasn't actually happened yet, so it shouldn't have
a Date yet. I need to blank out this value that was previously set in
the Person object...
if (some criteria)
{ timeArr[event] = null; }
But since these references don't seem to propogate backwards, nulling
one of the array elements doesn't affect the original property. That's
the *whole purpose* of reference vs value... a reference is a pointer to
memory space... so if I null that memory space it should affect all the
vars pointing to that memory space.
Does that make more sense?
Darren
To: [EMAIL PROTECTED] ups.com
From: [EMAIL PROTECTED] com
Date: Thu, 17 Jul 2008 11:30:29 +1000
Subject: Re: [flexcoders] Array reference vs values
When you do this:
var date:Date = new Date();
You're creating an instance of Date and a reference to it named "date".
When you do this:
var ref:Date = arr[0] as Date;
You're creating another reference to the same instance, this time your
reference is named "ref". So when you set ref = null, you're making
"ref" point to nothing. "date" and "arr[0]" remain unchanged. You don't
need to, nor can you remove the date instance created above. That's the
job of the garbage collector.
-Josh
On Thu, Jul 17, 2008 at 11:25 AM, Darren Houle <[EMAIL PROTECTED] com
<mailto:[EMAIL PROTECTED]> > wrote:
This might be a basic AS question, but I encountered it building a
Flex app, so...
I create a Date
var date:Date = new Date();
I create an Array
var arr:Array = new Array();
I set the first element of the array equal to the date
arr[0] = date;
I create another date variable that refers to the first array element
var ref:Date = arr[0] as Date;
if I trace("date= "+date+", arr[0]="+arr[ 0]+", ref="+ref) I get
date=Wed Jul 16 21:04:45 GMT-0400 2008, arr[0]=Wed Jul 16 21:04:45
GMT-0400 2008, ref=Wed Jul 16 21:04:45 GMT-0400 2008
Now I null out the ref variable
ref=null;
Since AS uses references instead of values I would expect to null out
the original date, but no...
If I trace("date= "+date+", arr[0]="+arr[ 0]+", ref="+ref) I now get
date=Wed Jul 16 21:04:45 GMT-0400 2008, arr[0]=Wed Jul 16 21:04:45
GMT-0400 2008, ref=null
I thought everything was a reference in AS? Shouldn't nulling ref
also null arr[0] which would null out date?
Ultimately.. . I have a custom object that has several fields each
cont
RE: [flexcoders] Array reference vs values
Darren,
Josh seems to have resolved your problem, but if you're interested,
here's a brief discussion of how references are working here:
>But since these references don't seem to propogate backwards, nulling
>one of the array elements doesn't affect the original property. That's
>the *whole purpose* of reference vs value... a reference is a pointer
>to memory space... so if I null that memory space it should affect all
>the vars pointing to that memory space.
The way references work in ActionScript (and in Java, C#, and most
others I'm familiar with), if you assign null to a reference, you are
not "null[ing] that memory space". You are nulling that *reference*.
It's your *reference* that now points to nothing--you're not actually
changing the contents of that memory location.
The behavior you're expecting could probably be achieved by another
level of indirection in references, but I'm not aware of any language
that actually does things this way. You could even achieve this in your
own code, by providing a wrapper class for Dates that exposes the
functions setDate(), getDate(), but Josh's suggestions is a better
solution.
--
Maciek Sakrejda
Truviso, Inc.
http://www.truviso.com
-Original Message-
From: Darren Houle <[EMAIL PROTECTED]>
Reply-To: flexcoders@yahoogroups.com
To: flexcoders@yahoogroups.com
Subject: RE: [flexcoders] Array reference vs values
Date: Wed, 16 Jul 2008 21:55:33 -0400
Josh
Yes, what you're describing is exactly what I described and is, in fact,
what it happening... but to say I don't ever need to do this? Well...
yes... I need to do this... and it has nothing to do with the garbage
collector.
Here, let me explain in another way
I have a custom object... lets say it's a Person object. It has various
properties, but several are Date types. These are all consecutive, like
a workflow, and I want to be able to address them in order via an
array... like this...
var person : Person = new Person();
person.wakeup = new Date();
person.breakfast = new Date();
person.lunch = new Date();
person.dinner = null;
person.bedtime = null;
var timeArr : Array = new Array();
timeArr[0] = person.wakeup;
timeArr[1] = person.breakfast;
timeArr[2] = person.lunch;
timeArr[3] = person.dinner;
timeArr[4] = person.bedtime;
Then some other code figures out where we are in the flow of the day's
events...
var status : int;
if (some criteria)
{ event = 2; }
But I determine lunch hasn't actually happened yet, so it shouldn't have
a Date yet. I need to blank out this value that was previously set in
the Person object...
if (some criteria)
{ timeArr[event] = null; }
But since these references don't seem to propogate backwards, nulling
one of the array elements doesn't affect the original property. That's
the *whole purpose* of reference vs value... a reference is a pointer to
memory space... so if I null that memory space it should affect all the
vars pointing to that memory space.
Does that make more sense?
Darren
____________
To: flexcoders@yahoogroups.com
From: [EMAIL PROTECTED]
Date: Thu, 17 Jul 2008 11:30:29 +1000
Subject: Re: [flexcoders] Array reference vs values
When you do this:
var date:Date = new Date();
You're creating an instance of Date and a reference to it named "date".
When you do this:
var ref:Date = arr[0] as Date;
You're creating another reference to the same instance, this time your
reference is named "ref". So when you set ref = null, you're making
"ref" point to nothing. "date" and "arr[0]" remain unchanged. You don't
need to, nor can you remove the date instance created above. That's the
job of the garbage collector.
-Josh
On Thu, Jul 17, 2008 at 11:25 AM, Darren Houle <[EMAIL PROTECTED]>
wrote:
This might be a basic AS question, but I encountered it building
a
Flex app, so...
I create a Date
var date:Date = new Date();
I create an Array
var arr:Array = new Array();
I set the first element of the array equal to the date
arr[0] = date;
I create another date variable that refers to the first array
element
var ref:Date = arr[0] as Date;
if I trace("date="+date+", arr[0]="+arr[0]+", ref="+ref) I get
date=Wed Jul 16 21:04:45 GMT-0400 2008, arr[0]=Wed Jul 16
21:04:45
GMT-0400 2008, ref=Wed Jul 16 21:04:45 GMT-0400 2008
Now I null out the ref variable
ref=null;
Since AS uses references instead of values I would expec
RE: [flexcoders] Array reference vs values
Josh
Okay, so here's what I did... var person : Person = new Person(); person.wakeup
= new Date();person.breakfast = new Date();person.lunch = new
Date();person.dinner = null;person.bedtime = null; var wfArr : Array = new
Array(); timeArr[0] = "wakeup";timeArr[1] = "breakfast";timeArr[2] =
"lunch";timeArr[3] = "dinner";timeArr[4] = "bedtime"; var event : int;if (some
criteria) { event = 2; } if (some criteria) {
person[timeArr[event]] = null; }and it works... person.lunch... aka
person["lunch"]... was set to null... thanks, you rock!! Darren
To: [EMAIL PROTECTED]: [EMAIL PROTECTED]: Thu, 17 Jul 2008 12:18:35
+1000Subject: Re: [flexcoders] Array reference vs values
On Thu, Jul 17, 2008 at 11:55 AM, Darren Houle <[EMAIL PROTECTED]> wrote:
Josh Yes, what you're describing is exactly what I described and is, in fact,
what it happening... but to say I don't ever need to do this? Well... yes... I
need to do this... and it has nothing to do with the garbage collector. Here,
let me explain in another way I have a custom object... lets say it's a
Person object. It has various properties, but several are Date types. These
are all consecutive, like a workflow, and I want to be able to address them in
order via an array... like this... var person : Person = new Person();
person.wakeup = new Date();person.breakfast = new Date();person.lunch = new
Date();person.dinner = null;person.bedtime = null; var timeArr : Array = new
Array(); timeArr[0] = person.wakeup;timeArr[1] = person.breakfast;timeArr[2] =
person.lunch;timeArr[3] = person.dinner;timeArr[4] = person.bedtime; Then some
other code figures out where we are in the flow of the day's events... var
status : int;if (some criteria) { event = 2; } But I determine lunch
hasn't actually happened yet, so it shouldn't have a Date yet. I need to blank
out this value that was previously set in the Person object... if (some
criteria) { timeArr[event] = null; } But since these references don't
seem to propogate backwards, nulling one of the array elements doesn't affect
the original property. That's the *whole purpose* of reference vs value... a
reference is a pointer to memory space... so if I null that memory space it
should affect all the vars pointing to that memory space. Does that make more
sense?DarrenI think so. But you're definitely going about it the wrong way -
hear me out:In ECMAScript, you can access any public field by indexing its name
as a string. Now assuming person has these fields, and you want to be able to
access them (and mess with them) in order. There's a few ways to do this:const
fieldOrder : Array = ['wakeup','breakfast','lunch','dinner',
'bedtime', ];Then you can do this:trace(myPerson.lunch); // ==
date.toString()myPerson[fieldOrder[2]] = null;trace(myPerson.lunch); // ==
nullBut while you can mute that instance of date, you can't delete it. It
defeats the purpose of garbage collection (and probably makes it a lot harder
to implement).If say, myPerson is *dynamic* either by the dynamic keyword on
the class definition, or because it's created with "{}" instead of "new
ClassName()", you can also do thisdelete
myPerson[fieldOrder[2]];trace(myPerson.lunch); // === undefined, or an
exception is thrown depending on various conditions of myPerson :)This will
completely remove the "lunch" field from the myPerson instance, but the Date
instance itself will still be sitting around waiting for garbage
collection.-Josh-- "Therefore, send not to know For whom the bell tolls. It
tolls for thee.":: Josh 'G-Funk' McDonald:: 0437 221 380 :: [EMAIL PROTECTED]
Re: [flexcoders] Array reference vs values
BWAHAHAHAHAHA! *wipes tear* That's awesome :) On Thu, Jul 17, 2008 at 12:53 PM, Sid Maskit <[EMAIL PROTECTED]> wrote: > Oops. Where my speech recognition software wrote "teen reference", it > should read "dereference". > -- "Therefore, send not to know For whom the bell tolls. It tolls for thee." :: Josh 'G-Funk' McDonald :: 0437 221 380 :: [EMAIL PROTECTED]
Re: [flexcoders] Array reference vs values
Oops. Where my speech recognition software wrote "teen reference", it should
read "dereference".
- Original Message
From: Sid Maskit <[EMAIL PROTECTED]>
To: flexcoders@yahoogroups.com
Sent: Wednesday, July 16, 2008 7:50:07 PM
Subject: Re: [flexcoders] Array reference vs values
It has been a while since I worked in C++, but I am pretty sure that you are
incorrect about references. If I remember correctly, C++ has a distinction
between pointers and references where a pointer points at a specific memory
address, but a reference is an alias for another variable, and that variable
might or might not itself be a pointer. The actual value of a pointer is a
memory address, but the value of a reference is the value of whatever variable
it refers to. In order to get the value of the object at the memory address,
one has to teen reference the pointer. These differences occur because pointers
and references used different mechanisms.
Like most, maybe all, more recent languages, ActionScript has references, but
not pointers.
A reference is simply an alias which gives one access to some object. It is
sort of like a telephone connection to the object: i.e. you can use it to set
or get the value of the object; but hanging up the phone only breaks the
connection, it does not make the object go away. You never have access to
memory addresses.
When an object has no references to it, it becomes eligible for garbage
collection. There is no way to determine when an object will in fact be garbage
collected.
Applying this to the system you are describing, things look like this. (For
simplicity, I will only deal with one of your dates.)
var person:Person = new Person();
Assuming that you are not assigning default values in your class, at this point
person.breakfast is null.
person.breakfast = new Date();
Now person.breakfast refers to the newly created date object: i.e. the date
object now has one reference to it.
timeArr[1] = person.breakfast;
Now timeArr[1] refers to the same date object as does person.breakfast: i.e.
the date object now has two references to it.
You could now access the date object by using either reference, and each of
them would give you the same information, and the same ability to manipulate
the date object.
However, setting a reference to null, or to a different object, is essentially
hanging up the telephone, and dialing a new number. This will connect the
variable you are using to that new object, but has no effect on other variables
referring to the previous object.
timeArr[1] = null;
Now timeArr[1] no longer refers to anything, but person.breakfast continues to
refer to the original date object.
Perhaps the key detail here is that what we have is to variables that refer to
the same object, but those variables have no relationship with one another.
This is one of the fundamental aspects of how object-oriented programming
works. I would not say that one could not have a system where having two
variables refer to the same object would put them into a relationship with one
another, but only that that would be a very different system from the one we
have.
Having said that, I would say that you are going to need to have a way of
directly accessing your person object if you want to set one or more of its
properties to null.
- Original Message
From: Darren Houle <[EMAIL PROTECTED] com>
To: [EMAIL PROTECTED] ups.com
Sent: Wednesday, July 16, 2008 6:55:33 PM
Subject: RE: [flexcoders] Array reference vs values
Josh
Yes, what you're describing is exactly what I described and is, in fact, what
it happening... but to say I don't ever need to do this? Well... yes... I need
to do this... and it has nothing to do with the garbage collector.
Here, let me explain in another way
I have a custom object... lets say it's a Person object. It has various
properties, but several are Date types. These are all consecutive, like a
workflow, and I want to be able to address them in order via an array... like
this...
var person : Person = new Person();
person.wakeup = new Date();
person.breakfast = new Date();
person.lunch = new Date();
person.dinner = null;
person.bedtime = null;
var timeArr : Array = new Array();
timeArr[0] = person.wakeup;
timeArr[1] = person.breakfast;
timeArr[2] = person.lunch;
timeArr[3] = person.dinner;
timeArr[4] = person.bedtime;
Then some other code figures out where we are in the flow of the day's events...
var status : int;
if (some criteria)
{ event = 2; }
But I determine lunch hasn't actually happened yet, so it shouldn't have a Date
yet. I need to blank out this value that was previously set in the Person
object...
if (some criteria)
{ timeArr[event] = null; }
But since these references don't seem to propogate backwards, nulling one of
the array elements doesn't affect the original property
Re: [flexcoders] Array reference vs values
It has been a while since I worked in C++, but I am pretty sure that you are
incorrect about references. If I remember correctly, C++ has a distinction
between pointers and references where a pointer points at a specific memory
address, but a reference is an alias for another variable, and that variable
might or might not itself be a pointer. The actual value of a pointer is a
memory address, but the value of a reference is the value of whatever variable
it refers to. In order to get the value of the object at the memory address,
one has to teen reference the pointer. These differences occur because pointers
and references used different mechanisms.
Like most, maybe all, more recent languages, ActionScript has references, but
not pointers.
A reference is simply an alias which gives one access to some object. It is
sort of like a telephone connection to the object: i.e. you can use it to set
or get the value of the object; but hanging up the phone only breaks the
connection, it does not make the object go away. You never have access to
memory addresses.
When an object has no references to it, it becomes eligible for garbage
collection. There is no way to determine when an object will in fact be garbage
collected.
Applying this to the system you are describing, things look like this. (For
simplicity, I will only deal with one of your dates.)
var person:Person = new Person();
Assuming that you are not assigning default values in your class, at this point
person.breakfast is null.
person.breakfast = new Date();
Now person.breakfast refers to the newly created date object: i.e. the date
object now has one reference to it.
timeArr[1] = person.breakfast;
Now timeArr[1] refers to the same date object as does person.breakfast: i.e.
the date object now has two references to it.
You could now access the date object by using either reference, and each of
them would give you the same information, and the same ability to manipulate
the date object.
However, setting a reference to null, or to a different object, is essentially
hanging up the telephone, and dialing a new number. This will connect the
variable you are using to that new object, but has no effect on other variables
referring to the previous object.
timeArr[1] = null;
Now timeArr[1] no longer refers to anything, but person.breakfast continues to
refer to the original date object.
Perhaps the key detail here is that what we have is to variables that refer to
the same object, but those variables have no relationship with one another.
This is one of the fundamental aspects of how object-oriented programming
works. I would not say that one could not have a system where having two
variables refer to the same object would put them into a relationship with one
another, but only that that would be a very different system from the one we
have.
Having said that, I would say that you are going to need to have a way of
directly accessing your person object if you want to set one or more of its
properties to null.
- Original Message
From: Darren Houle <[EMAIL PROTECTED]>
To: flexcoders@yahoogroups.com
Sent: Wednesday, July 16, 2008 6:55:33 PM
Subject: RE: [flexcoders] Array reference vs values
Josh
Yes, what you're describing is exactly what I described and is, in fact, what
it happening... but to say I don't ever need to do this? Well... yes... I need
to do this... and it has nothing to do with the garbage collector.
Here, let me explain in another way
I have a custom object... lets say it's a Person object. It has various
properties, but several are Date types. These are all consecutive, like a
workflow, and I want to be able to address them in order via an array... like
this...
var person : Person = new Person();
person.wakeup = new Date();
person.breakfast = new Date();
person.lunch = new Date();
person.dinner = null;
person.bedtime = null;
var timeArr : Array = new Array();
timeArr[0] = person.wakeup;
timeArr[1] = person.breakfast;
timeArr[2] = person.lunch;
timeArr[3] = person.dinner;
timeArr[4] = person.bedtime;
Then some other code figures out where we are in the flow of the day's events...
var status : int;
if (some criteria)
{ event = 2; }
But I determine lunch hasn't actually happened yet, so it shouldn't have a Date
yet. I need to blank out this value that was previously set in the Person
object...
if (some criteria)
{ timeArr[event] = null; }
But since these references don't seem to propogate backwards, nulling one of
the array elements doesn't affect the original property. That's the *whole
purpose* of reference vs value... a reference is a pointer to memory space...
so if I null that memory space it should affect all the vars pointing to that
memory space.
Does that make more sense?
Darren
To: [EMAIL PROTECTED] ups.com
From: [EMAIL PROTECTED
Re: [flexcoders] Array reference vs values
On Thu, Jul 17, 2008 at 11:55 AM, Darren Houle <[EMAIL PROTECTED]> wrote:
> Josh
>
> Yes, what you're describing is exactly what I described and is, in fact,
> what it happening... but to say I don't ever need to do this? Well...
> yes... I need to do this... and it has nothing to do with the garbage
> collector.
>
> Here, let me explain in another way
>
> I have a custom object... lets say it's a Person object. It has various
> properties, but several are Date types. These are all consecutive, like a
> workflow, and I want to be able to address them in order via an array...
> like this...
>
> var person : Person = new Person();
>
> person.wakeup = new Date();
> person.breakfast = new Date();
> person.lunch = new Date();
> person.dinner = null;
> person.bedtime = null;
>
> var timeArr : Array = new Array();
>
> timeArr[0] = person.wakeup;
> timeArr[1] = person.breakfast;
> timeArr[2] = person.lunch;
> timeArr[3] = person.dinner;
> timeArr[4] = person.bedtime;
>
>
> Then some other code figures out where we are in the flow of the day's
> events...
>
> var status : int;
> if (some criteria)
> { event = 2; }
>
> But I determine lunch hasn't actually happened yet, so it shouldn't have a
> Date yet. I need to blank out this value that was previously set in the
> Person object...
>
> if (some criteria)
> { timeArr[event] = null; }
>
> But since these references don't seem to propogate backwards, nulling one
> of the array elements doesn't affect the original property. That's the
> *whole purpose* of reference vs value... a reference is a pointer to memory
> space... so if I null that memory space it should affect all the vars
> pointing to that memory space.
>
> Does that make more sense?
>
> Darren
>
>
>
I think so. But you're definitely going about it the wrong way - hear me
out:
In ECMAScript, you can access any public field by indexing its name as a
string. Now assuming person has these fields, and you want to be able to
access them (and mess with them) in order. There's a few ways to do this:
const fieldOrder : Array =
[
'wakeup',
'breakfast',
'lunch',
'dinner',
'bedtime',
];
Then you can do this:
trace(myPerson.lunch); // == date.toString()
myPerson[fieldOrder[2]] = null;
trace(myPerson.lunch); // == null
But while you can mute that instance of date, you can't delete it. It
defeats the purpose of garbage collection (and probably makes it a lot
harder to implement).
If say, myPerson is *dynamic* either by the dynamic keyword on the class
definition, or because it's created with "{}" instead of "new ClassName()",
you can also do this
delete myPerson[fieldOrder[2]];
trace(myPerson.lunch); // === undefined, or an exception is thrown depending
on various conditions of myPerson :)
This will completely remove the "lunch" field from the myPerson instance,
but the Date instance itself will still be sitting around waiting for
garbage collection.
-Josh
--
"Therefore, send not to know For whom the bell tolls. It tolls for thee."
:: Josh 'G-Funk' McDonald
:: 0437 221 380 :: [EMAIL PROTECTED]
Re: [flexcoders] Array reference vs values
I think you may be able to do what you are doing by using the ByteArray class
but I would wait for someone that knows more than me. The only things that get
passed by reference is any class that inherits from an Object and Array is a
native Flash player class in C++.
- Original Message
From: Sherif Abdou <[EMAIL PROTECTED]>
To: flexcoders@yahoogroups.com
Sent: Wednesday, July 16, 2008 8:59:54 PM
Subject: Re: [flexcoders] Array reference vs values
If i remember correctly since I am mixing too much C++,ActionScript, Coldfusion
and learning them all the same time. Any of the primitive stuff in Actionscript
get passed only by value and not by reference so you can't do what you are
doing.
- Original Message
From: Darren Houle <[EMAIL PROTECTED] com>
To: [EMAIL PROTECTED] ups.com
Sent: Wednesday, July 16, 2008 8:55:33 PM
Subject: RE: [flexcoders] Array reference vs values
Josh
Yes, what you're describing is exactly what I described and is, in fact, what
it happening... but to say I don't ever need to do this? Well... yes... I need
to do this... and it has nothing to do with the garbage collector.
Here, let me explain in another way
I have a custom object... lets say it's a Person object. It has various
properties, but several are Date types. These are all consecutive, like a
workflow, and I want to be able to address them in order via an array... like
this...
var person : Person = new Person();
person.wakeup = new Date();
person.breakfast = new Date();
person.lunch = new Date();
person.dinner = null;
person.bedtime = null;
var timeArr : Array = new Array();
timeArr[0] = person.wakeup;
timeArr[1] = person.breakfast;
timeArr[2] = person.lunch;
timeArr[3] = person.dinner;
timeArr[4] = person.bedtime;
Then some other code figures out where we are in the flow of the day's events...
var status : int;
if (some criteria)
{ event = 2; }
But I determine lunch hasn't actually happened yet, so it shouldn't have a Date
yet. I need to blank out this value that was previously set in the Person
object...
if (some criteria)
{ timeArr[event] = null; }
But since these references don't seem to propogate backwards, nulling one of
the array elements doesn't affect the original property. That's the *whole
purpose* of reference vs value... a reference is a pointer to memory space...
so if I null that memory space it should affect all the vars pointing to that
memory space.
Does that make more sense?
Darren
To: [EMAIL PROTECTED] ups.com
From: [EMAIL PROTECTED] com
Date: Thu, 17 Jul 2008 11:30:29 +1000
Subject: Re: [flexcoders] Array reference vs values
When you do this:
var date:Date = new Date();
You're creating an instance of Date and a reference to it named "date".
When you do this:
var ref:Date = arr[0] as Date;
You're creating another reference to the same instance, this time your
reference is named "ref". So when you set ref = null, you're making "ref" point
to nothing. "date" and "arr[0]" remain unchanged. You don't need to, nor can
you remove the date instance created above. That's the job of the garbage
collector.
-Josh
On Thu, Jul 17, 2008 at 11:25 AM, Darren Houle <[EMAIL PROTECTED] com> wrote:
This might be a basic AS question, but I encountered it building a
Flex app, so...
I create a Date
var date:Date = new Date();
I create an Array
var arr:Array = new Array();
I set the first element of the array equal to the date
arr[0] = date;
I create another date variable that refers to the first array element
var ref:Date = arr[0] as Date;
if I trace("date= "+date+", arr[0]="+arr[ 0]+", ref="+ref) I get
date=Wed Jul 16 21:04:45 GMT-0400 2008, arr[0]=Wed Jul 16 21:04:45
GMT-0400 2008, ref=Wed Jul 16 21:04:45 GMT-0400 2008
Now I null out the ref variable
ref=null;
Since AS uses references instead of values I would expect to null out
the original date, but no...
If I trace("date= "+date+", arr[0]="+arr[ 0]+", ref="+ref) I now get
date=Wed Jul 16 21:04:45 GMT-0400 2008, arr[0]=Wed Jul 16 21:04:45
GMT-0400 2008, ref=null
I thought everything was a reference in AS? Shouldn't nulling ref
also null arr[0] which would null out date?
Ultimately.. . I have a custom object that has several fields each
containing a Date. I create an array and make each element in the
array = each Date in the custom obj. I need to be able to null an
array element and have it carry backwards into the object and null
out the original Date. Any ideas? Am I missing something really
obvious?
- - --
--
Flexcoders Mailing List
FAQ: http://groups. yahoo.com/ group/flexcoders /files/flexcoder sFAQ.txt
Search Archives:
Re: [flexcoders] Array reference vs values
If i remember correctly since I am mixing too much C++,ActionScript,Coldfusion
and learning them all the same time. Any of the primitive stuff in Actionscript
get passed only by value and not by reference so you can't do what you are
doing.
- Original Message
From: Darren Houle <[EMAIL PROTECTED]>
To: flexcoders@yahoogroups.com
Sent: Wednesday, July 16, 2008 8:55:33 PM
Subject: RE: [flexcoders] Array reference vs values
Josh
Yes, what you're describing is exactly what I described and is, in fact, what
it happening... but to say I don't ever need to do this? Well... yes... I need
to do this... and it has nothing to do with the garbage collector.
Here, let me explain in another way
I have a custom object... lets say it's a Person object. It has various
properties, but several are Date types. These are all consecutive, like a
workflow, and I want to be able to address them in order via an array... like
this...
var person : Person = new Person();
person.wakeup = new Date();
person.breakfast = new Date();
person.lunch = new Date();
person.dinner = null;
person.bedtime = null;
var timeArr : Array = new Array();
timeArr[0] = person.wakeup;
timeArr[1] = person.breakfast;
timeArr[2] = person.lunch;
timeArr[3] = person.dinner;
timeArr[4] = person.bedtime;
Then some other code figures out where we are in the flow of the day's events...
var status : int;
if (some criteria)
{ event = 2; }
But I determine lunch hasn't actually happened yet, so it shouldn't have a Date
yet. I need to blank out this value that was previously set in the Person
object...
if (some criteria)
{ timeArr[event] = null; }
But since these references don't seem to propogate backwards, nulling one of
the array elements doesn't affect the original property. That's the *whole
purpose* of reference vs value... a reference is a pointer to memory space...
so if I null that memory space it should affect all the vars pointing to that
memory space.
Does that make more sense?
Darren
To: [EMAIL PROTECTED] ups.com
From: [EMAIL PROTECTED] com
Date: Thu, 17 Jul 2008 11:30:29 +1000
Subject: Re: [flexcoders] Array reference vs values
When you do this:
var date:Date = new Date();
You're creating an instance of Date and a reference to it named "date".
When you do this:
var ref:Date = arr[0] as Date;
You're creating another reference to the same instance, this time your
reference is named "ref". So when you set ref = null, you're making "ref" point
to nothing. "date" and "arr[0]" remain unchanged. You don't need to, nor can
you remove the date instance created above. That's the job of the garbage
collector.
-Josh
On Thu, Jul 17, 2008 at 11:25 AM, Darren Houle <[EMAIL PROTECTED] com> wrote:
This might be a basic AS question, but I encountered it building a
Flex app, so...
I create a Date
var date:Date = new Date();
I create an Array
var arr:Array = new Array();
I set the first element of the array equal to the date
arr[0] = date;
I create another date variable that refers to the first array element
var ref:Date = arr[0] as Date;
if I trace("date= "+date+", arr[0]="+arr[ 0]+", ref="+ref) I get
date=Wed Jul 16 21:04:45 GMT-0400 2008, arr[0]=Wed Jul 16 21:04:45
GMT-0400 2008, ref=Wed Jul 16 21:04:45 GMT-0400 2008
Now I null out the ref variable
ref=null;
Since AS uses references instead of values I would expect to null out
the original date, but no...
If I trace("date= "+date+", arr[0]="+arr[ 0]+", ref="+ref) I now get
date=Wed Jul 16 21:04:45 GMT-0400 2008, arr[0]=Wed Jul 16 21:04:45
GMT-0400 2008, ref=null
I thought everything was a reference in AS? Shouldn't nulling ref
also null arr[0] which would null out date?
Ultimately.. . I have a custom object that has several fields each
containing a Date. I create an array and make each element in the
array = each Date in the custom obj. I need to be able to null an
array element and have it carry backwards into the object and null
out the original Date. Any ideas? Am I missing something really
obvious?
- - --
--
Flexcoders Mailing List
FAQ: http://groups. yahoo.com/ group/flexcoders /files/flexcoder sFAQ.txt
Search Archives: http://www.mail- archive.com/ flexcoders% 40yahoogroups.
comYahoo! Groups Links
--
"Therefore, send not to know For whom the bell tolls. It tolls for thee."
:: Josh 'G-Funk' McDonald
:: 0437 221 380 :: [EMAIL PROTECTED] com
RE: [flexcoders] Array reference vs values
Josh
Yes, what you're describing is exactly what I described and is, in fact, what
it happening... but to say I don't ever need to do this? Well... yes... I need
to do this... and it has nothing to do with the garbage collector.
Here, let me explain in another way
I have a custom object... lets say it's a Person object. It has various
properties, but several are Date types. These are all consecutive, like a
workflow, and I want to be able to address them in order via an array... like
this...
var person : Person = new Person();
person.wakeup = new Date();person.breakfast = new Date();person.lunch = new
Date();person.dinner = null;person.bedtime = null;
var timeArr : Array = new Array();
timeArr[0] = person.wakeup;timeArr[1] = person.breakfast;timeArr[2] =
person.lunch;timeArr[3] = person.dinner;timeArr[4] = person.bedtime;
Then some other code figures out where we are in the flow of the day's events...
var status : int;
if (some criteria)
{ event = 2; }
But I determine lunch hasn't actually happened yet, so it shouldn't have a Date
yet. I need to blank out this value that was previously set in the Person
object...
if (some criteria)
{ timeArr[event] = null; }
But since these references don't seem to propogate backwards, nulling one of
the array elements doesn't affect the original property. That's the *whole
purpose* of reference vs value... a reference is a pointer to memory space...
so if I null that memory space it should affect all the vars pointing to that
memory space.
Does that make more sense?Darren
To: [EMAIL PROTECTED]: [EMAIL PROTECTED]: Thu, 17 Jul 2008 11:30:29
+1000Subject: Re: [flexcoders] Array reference vs values
When you do this: var date:Date = new Date();You're creating an instance of
Date and a reference to it named "date".When you do this: var ref:Date =
arr[0] as Date;You're creating another reference to the same instance, this
time your reference is named "ref". So when you set ref = null, you're making
"ref" point to nothing. "date" and "arr[0]" remain unchanged. You don't need
to, nor can you remove the date instance created above. That's the job of the
garbage collector.-Josh
On Thu, Jul 17, 2008 at 11:25 AM, Darren Houle <[EMAIL PROTECTED]> wrote:
Re: [flexcoders] Array reference vs values
When you do this:
var date:Date = new Date();
You're creating an instance of Date and a reference to it named "date".
When you do this:
var ref:Date = arr[0] as Date;
You're creating another reference to the same instance, this time your
reference is named "ref". So when you set ref = null, you're making "ref"
point to nothing. "date" and "arr[0]" remain unchanged. You don't need to,
nor can you remove the date instance created above. That's the job of the
garbage collector.
-Josh
On Thu, Jul 17, 2008 at 11:25 AM, Darren Houle <[EMAIL PROTECTED]> wrote:
> This might be a basic AS question, but I encountered it building a
> Flex app, so...
>
> I create a Date
>
>var date:Date = new Date();
>
> I create an Array
>
>var arr:Array = new Array();
>
> I set the first element of the array equal to the date
>
>arr[0] = date;
>
> I create another date variable that refers to the first array element
>
>var ref:Date = arr[0] as Date;
>
> if I trace("date="+date+", arr[0]="+arr[0]+", ref="+ref) I get
>
> date=Wed Jul 16 21:04:45 GMT-0400 2008, arr[0]=Wed Jul 16 21:04:45
> GMT-0400 2008, ref=Wed Jul 16 21:04:45 GMT-0400 2008
>
> Now I null out the ref variable
>
>ref=null;
>
> Since AS uses references instead of values I would expect to null out
> the original date, but no...
>
> If I trace("date="+date+", arr[0]="+arr[0]+", ref="+ref) I now get
>
> date=Wed Jul 16 21:04:45 GMT-0400 2008, arr[0]=Wed Jul 16 21:04:45
> GMT-0400 2008, ref=null
>
> I thought everything was a reference in AS? Shouldn't nulling ref
> also null arr[0] which would null out date?
>
> Ultimately... I have a custom object that has several fields each
> containing a Date. I create an array and make each element in the
> array = each Date in the custom obj. I need to be able to null an
> array element and have it carry backwards into the object and null
> out the original Date. Any ideas? Am I missing something really
> obvious?
>
>
>
>
> --
> Flexcoders Mailing List
> FAQ: http://groups.yahoo.com/group/flexcoders/files/flexcodersFAQ.txt
> Search Archives:
> http://www.mail-archive.com/flexcoders%40yahoogroups.comYahoo! Groups
> Links
>
>
>
>
--
"Therefore, send not to know For whom the bell tolls. It tolls for thee."
:: Josh 'G-Funk' McDonald
:: 0437 221 380 :: [EMAIL PROTECTED]
