Code example for function/delegate as template argument ?

[H. S. Teoh via Digitalmars-d-learn]

On Wed, May 04, 2016 at 06:21:36AM +0000, chmike via Digitalmars-d-learn wrote:
> Hello,
> 
> I failed to find some code example for a template class/struct that
> accept a function/delegate as template argument. All examples I could
> find use simple value types like int or double.

The usual way is to use an alias argument:

	class MyClass(alias fun)
		if (is(typeof(fun(0)))) // assuming fun takes 1 int argument
	{
		void method() {
			fun(0);
		}
	}


> I piggy bag another question. Defining a function/delegate as function
> argument is shown in examples. What I could not find is how would I
> pass an object instance with a method to call ? In C++ we use
> std::bind. How do we do that in D ?

You probably need a delegate, since a function (== function pointer) in
D is a pointer to a (module-global) function with no context. If you
need a context, e.g., an object instance, you need a delegate. Example:

	class C {
		void method(int x) {
			import std.stdio;
			writeln("bing!");
		}
	}
	void fun(void delegate(int) dg) {
		dg(1);
	}
	void main() {
		auto c = new C;
		fun(&c.method);
	}


T

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