Auto-Implemented properties

[michaelc37]

On Sunday, 6 January 2013 at 11:32:40 UTC, Jacob Carlborg wrote:
> On 2013-01-05 23:40, michaelc37 wrote:
>> i was trying to make a D template to mimic auto-implemented
>> properties in c#.
>>
>> I think i got it to work but when i tried to give the template 
>> a
>> more meaning full name like AutoImplementedProperty i get a
>> compile error "a.title is not an lvalue".
>> Is this a bug?
>> Is there a more suitable way of doing this?
>>
>> c# e.g:
>> class Bar
>> {
>>     public string Title { get; set; }
>> }
>>
>> my attempt:
>> class Bar
>> {
>>     alias autoproperty!(string, "get", "set") title
>> }
>>
>> template autoproperty(T, args...)
>> {
>>     import std.typetuple;
>>     @property
>>     {
>>         private T _name;
>>         static if (args.length)
>>         {
>>             static if (staticIndexOf!("get", args) > -1)
>>             {
>>                 public T autoproperty()
>>                 {
>>                     return _name;
>>                 }
>>             }
>>
>>             static if (staticIndexOf!("set", args) > -1)
>>             {
>>                 public void autoproperty(T value)
>>                 {
>>                     _name = value;
>>                 }
>>             }
>>
>>         }
>>     }
>> }
>>
>> void main(string[] args)
>> {
>>     Bar a = new Bar();
>>     a.title = "asf";
>>     writefln(a.title);
>>
>>     return;
>> }
>
> This won't work like you think it will. All instances of "Bar" 
> will share the same "_name" variable.
>
> You need to use a mixin. This pass:
>
> void main ()
> {
>     Bar a = new Bar();
>     a.title = "asf";
>
>     Bar b = new Bar;
>     assert(b.title == a.title);
> }

Yea i realized that later, but the only fix i could come up with 
required me passing the property name in the template parameters, 
so the declaration has changed a bit.

second attempt;

class Bar
{
	public mixin autoproperty!(string, "title", "get", "set");
	public mixin autoproperty!(string, "description", "get", "set");
}

mixin template autoproperty(T, alias propertyName, args...)
{
	import std.typetuple;

	mixin("private T _" ~ propertyName ~ ";");
		
	@property
	{		
		static if (args.length)
		{
			static if (staticIndexOf!("get", args) > -1)
			{
				mixin("
				T " ~ propertyName ~ "()
				{
					return _" ~ propertyName ~ ";					
				}");
			}
	
			static if (staticIndexOf!("set", args) > -1)
			{
				mixin("
				void " ~ propertyName ~ "(T value)
				{
					_" ~ propertyName ~ " = value;
				}");
			}			
		}
	}	
}