Delegates and classes for custom code.

[arturg]

On Wednesday, 18 April 2018 at 01:12:33 UTC, Chris Katko wrote:
> That was all pseudo-code typed by hand.
>
> I got my code to work today. I don't know if it's the prettiest 
> it can be, but it works:
>
> // TESTING ACCESS TO the OWNING function
> //-------------------------------------------
> class test_window
> 	{
> 	float x;
> 	float y;
> 	
> 	void draw_text(string text)
> 		{
> 		writeln(text);		
> 		}
>
> 	this( void function(test_window) onDraw  )
> 		{	
> 		this.onDraw = onDraw;
> 		}
>
> 	void run() //called every frame
> 		{
> 		onDraw(this);
> 		}
>
> 	void function (test_window) onDraw;
> 	}
>
>
> void test_dialog()
> 	{
> 	auto t = new test_window(function void(test_window ptr)
> 		{
> 		with(ptr)
> 			{
> 			draw_text( format("Hello, world. [x,y]=[%f,%f]", x, y));
> 			}
> 		});
> 		
> 	t.run();
> 	}
>
>
>
>
>
> And a second attempt/version:
>
>
>
>
>
> // TESTING ACCESS to anything
> // ----------------------------------------------------------
>
> struct data_to_access_t
> 	{
> 	int tacos;
> 	}
>
> struct data_to_access2_t
> 	{
> 	struct beans
> 		{
> 		int x;
> 		};
> 		
> 	beans b;
> 	}
>
> class abc(T)
> 	{
> 	int x;
> 	void delegate(T) run_delegate;
> 		
> 	T data;
> 		
> 	this(T t, void delegate(T) d)
> 		{
> 		data = t;
> 		run_delegate = d;
> 		}
> 	
> 	void execute()
> 		{
> 		run_delegate(data);
> 		}
> 	}
>
> void test_dialog_anything()
> 	{	
> 	data_to_access_t  d;
> 	data_to_access2_t d2;
> 	d.tacos = 4;
> 	d2.b.x  = 5;
>
> 	auto x = new abc!data_to_access_t ( d, (d) => writefln("test  
> %d", d.tacos)  );
> 	auto y = new abc!data_to_access_t ( d, (d){writefln("test  
> %d", d.tacos);}  );
> 	auto z = new abc!data_to_access2_t(d2, delegate void 
> (d2){writefln("test2 %d", d2.b.x);}  );
> 	
> 	x.execute();
> 	y.execute();
> 	z.execute();
> 	}
>
>
>
>
>
> My only questions are:
>
>  -  is there any way to make it "smart" enough to take the type 
> of the argument, instead of me manually giving it a type.
>
> 	auto x = new abc!data_to_access_t ( d, (d) => writefln("test  
> %d", d.tacos)  );
> becomes
> 	auto x = new abc( d, (d) => writefln("test  %d", d.tacos)  );
>
>  - Is there any way to eliminate the first d? Which is 
> essentially a "this" pointer.
>
> 	auto x = new abc!data_to_access_t ( d, (d) => writefln("test  
> %d", d.tacos)  );
> becomes
> 	auto x = new abc!data_to_access_t ( (d) => writefln("test  
> %d", d.tacos)  );
>
>  - And preferably, if possible, both. But I'll take what I can 
> get.

is it this what you want?

    class A
    {
        int a;
        void delegate() onDraw;

        this(void delegate() dg)
        {
            onDraw = dg;
        }

        void drawText(string s)
        {
            s.writeln;
        }
    }

    void main()
    {
         A a;
         a = new A((){ a.a = 5; a.drawText("test"); "drawing 
all".writeln; });
     }

but if you do A a = new A((){ a.a = 5; ...});
the dg cant capture 'a' yet.
so maybe it would be better to just do:
A a = new A;
a.onDraw = (){ a.drawText("test"); "draw rest".writeln; };