Transparent cast from class to member pointer?

[Ali Çehreli]

On 04/14/2019 11:03 AM, Robert M. Münch wrote:
> struct IM;
> struct C {
>   IM *impl;
> };
> 
> int cInit(C* self);
> 
> class I {
>      C handler;
> 
>      this(){cInit(&handler);}
> }
> 
> Is there a simple way that I can use handler without the address-of 
> operator and automatically get *impl?
> 
> Something like:
> 
> class I {
>      C handler;
> 
>      this(){cInit(handler);}
> }
> 
> And later can use I in a way like this without having to define/write 
> explicit casts everywhere?
> 
> someFunc(C* self);
> 
> I myI;
> someFunc(myI);
> 
> 

'alias this' can do that:

struct IM;
struct C {
  IM *impl;
};

int cInit(C* self) {
   return 0;
}

class I {
     C handler;

     this(){cInit(&handler);}

   C* ptr() {               // <== ADDED
     return &handler;
   }

   alias ptr this;          // <== ADDED
}

void someFunc(C* self) {
}

void main() {
   I myI = new I();
   someFunc(myI);
}

Ali