Re: Template delegate/function ptr struct member

[Rikki Cattermole via Digitalmars-d-learn]

On 13/05/2014 7:28 p.m., ed wrote:
I'm porting some C++ code to D and a struct has the following member:
struct S
{
// ...
  //void* (*createMethod)();

void* function() createMethod;

}

I'd like to extend this as little to accept delegates for future use
without breakage to existing code...

Is it possible to template this so "createMethod" can be a delegate() or
function() of any type *and* have the compiler infer the type from ctor
parameters?

For example:
---
struct S(F)
{
     // ...
     F createMethod;
     this(alias F)() {createMethod = &F;}
}
static void* func() {return null;}

void main() {
     auto s1 = S(&func);
     auto s2 = S(&Object.classinfo.create);

     // s1 is S!(void* function())
     // s2 is S!(Object delegate() const);
}
---

Is this a good idea or am I way off?

Thanks,
ed

I would recommend going the route of property functions and using 
delegates as the default.

alias createMethodDel = void* delegate();
alias createMethodFunc = void* function();

struct S {
    private createMethodDel createMethod_;

    @property {
        createMethodDel createMethod() {
            return createMethod_;
        }

        void createMethod(createMethodDel func) {
            createMethod_ = func;
        }

        void createMethod(createMethodFunc func) {
            import std.functional : toDelegate;
            createMethod_ = toDelegate(func);
        }
    }
}

That way you know what you have access to is always callable and won't 
break any code.