Re: @property get/set or public varaible?
On Sunday, 4 December 2016 at 20:44:05 UTC, Jonathan M Davis
wrote:
On Sunday, December 04, 2016 15:30:22 vladdeSV via
Digitalmars-d-learn wrote:
Hello!
I have a question not directly related to D as it is with
coding standards.
My issue at hand is if I have one variable for a class, which I
want to be directly accessible for anything else, should it be
1. public, or
2. private, with @property get/setters?
From what I have been told is that variables should be
private.
But if I do not want to make any checks whatsoever when
setting a
variable, I see no benefit to the private approach.
Are there any other reasons to use get/setters?
This might not be usefull for ure current usecase but if you want
a property to behave like a field, it has to be a field.
So a boxed type might be better depending how much you want to
manage.
Here are some property like examples:
struct Prop(T)
{
private T value;
alias opCall this;
ref T opCall() { return value; }
ref T opCall(T val) { return value = val; }
string toString() { import std.conv: to; return
value.to!string; }
}
struct ReadOnly(T)
{
private T value;
alias opCall this;
T opCall() { return value; } // return a copy
string toString() { import std.conv: to; return
value.to!string; }
}
struct WriteOnly(T)
{
private T value;
void opAssign(T val) { value = val; }
string toString() { return typeof(this).stringof; }
}
// alternative write only so you can chain opCall
writeOnly(33)(56)(66);
struct AltWriteOnly(T)
{
private T value;
ref typeof(this) opCall(T val) { value = val; return this; }
string toString() { return typeof(this).stringof; }
}
struct FunProp(T) if(isSomeFunction!T)
{
private T value;
alias value this;
void opAssign(T val) { value = val; }
string toString() { return T.stringof; }
}
class Test
{
Prop!int someVal;
ReadOnly!string name;
WriteOnly!int someOtherVal;
FunProp!(void delegate(int)) funProp;
this()
{
name.value = "Test";
}
}
void main()
{
auto test = new Test;
test.someVal = 66;
test.someVal++;
test.someOtherVal = 100;
test.funProp = (int i) => i + test.someVal;
test.someVal.writeln;
test.name.writeln;
test.funProp(33).writeln;
test.funProp.writeln;
test.someOtherVal.writeln;
}
haven't done extencive tests with them but they can be used as
builing blocks, you can add other operator overloads to manage
other access to the value.
you can build better properties without @property :/
Re: @property get/set or public varaible?
On Sunday, December 04, 2016 15:30:22 vladdeSV via Digitalmars-d-learn wrote: > Hello! > > I have a question not directly related to D as it is with coding > standards. > > My issue at hand is if I have one variable for a class, which I > want to be directly accessible for anything else, should it be > 1. public, or > 2. private, with @property get/setters? > > From what I have been told is that variables should be private. > But if I do not want to make any checks whatsoever when setting a > variable, I see no benefit to the private approach. > > Are there any other reasons to use get/setters? The big reason to use getters and setters over public variables is that converting public variables to property functions is _not_ seemless. Property functions act like variables for some basic operations like assignment, but you try and do much more than that, and they start behaving drastically differently. For instance, what happens if someone takes the address of a property? Or passes it by reference? As long as that property is a member variable, it works like a variable, but if it's changed to a property function, then those operations either have different types and don't compile with existing code, or the operations don't work at all. Even basic operations such as ++ don't work with property functions. I'm sure that there are folks in the D community who favor using public variables rather than property functions if they're not going to do anything beyond getting or setting, but you're at serious risk of code breakage if you do - especially if you're doing it in an API that you're distributing to other people. For your own personal stuff or stuff that is internal to whatever project you're doing where you can change all of the code that uses the property, then it can work to use a public variable and then change the code later if necessary if and when it becomes a property function. And since most public variables don't get turned into property functions later, you probabably will only have to deal with code breakage rarely, and it will be easy for you to fix the few places where the property was used in a way that works for a public variable but not for a property function. But if you're distributing a library with a property that's a public variable, you can't change all of the code using that property, and changing it to a property function could easily break other people's code. So, do what you want for internal stuff, but don't use public member variables in libraries that you're distributing unless it's certain that they will never be anything but public variables. - Jonathan M Davis
Re: @property get/set or public varaible?
On Sunday, 4 December 2016 at 15:30:22 UTC, vladdeSV wrote: Are there any other reasons to use get/setters? basically, no. as you can omit parentheses in D, converting to getter/setter later should be seamless. the only reason to have getter/setter in your case is a situation where you may want to override 'em in child class. so if you are using class hierarchy, take some time to think if you will ever need such overrides.
Re: @property get/set or public varaible?
On Sunday, 4 December 2016 at 15:30:22 UTC, vladdeSV wrote: Hello! I have a question not directly related to D as it is with coding standards. My issue at hand is if I have one variable for a class, which I want to be directly accessible for anything else, should it be 1. public, or 2. private, with @property get/setters? From what I have been told is that variables should be private. But if I do not want to make any checks whatsoever when setting a variable, I see no benefit to the private approach. Are there any other reasons to use get/setters? Make the member variable public, if it serves your purpose. If (and when) you feel like taking some control over setting and getting its value, you will upgrade it to @property setter/getter, making the actual member variable private. For most reasonable use cases the upgrade should pass with no problems. ... If you envision such an upgrade possibility, try to keep away from taking your member variable address, and other not method-friendly operations, that might hold the upgrade back.
@property get/set or public varaible?
Hello! I have a question not directly related to D as it is with coding standards. My issue at hand is if I have one variable for a class, which I want to be directly accessible for anything else, should it be 1. public, or 2. private, with @property get/setters? From what I have been told is that variables should be private. But if I do not want to make any checks whatsoever when setting a variable, I see no benefit to the private approach. Are there any other reasons to use get/setters?
