Composite Pattern and simplificaton

[JS]

On Thursday, 4 July 2013 at 07:03:39 UTC, Baz wrote:
> On Wednesday, 3 July 2013 at 10:12:34 UTC, JS wrote:
>> Is there any nifty D features that allow one to simplify the 
>> composite pattern,
>>
>> e.g.,
>>
>>    class A : B
>>    {
>>        B b;
>>    }
>>
>> Where I would like to have class A's implementation of B be 
>> use b. This would avoid a lot of boilerplate code if just 
>> redirecting A's implementation of B to b.
>>
>> e.g.,
>>
>>   class A : B(use b)
>>   {
>>       B b;
>>   }
>>
>>
>> or maybe more D'ish
>>
>>   class A : B
>>   {
>>      B b;
>>      alias b A:B;
>>   }
>>
>> probably some fancy mixin could be used:
>>
>>   class A : B
>>   {
>>      B b;
>>      mixin simpleComposite(b);   // Just implements B with 
>> redirection to b
>>   }
>
> You can also try to overload opCast() in the container class, a 
> bit in the same fashion that the 'alias this' stuff (except 
> that alias this will not work with many sub classes). The idea 
> is exposed here:
>
> http://dpaste.dzfl.pl/33d1b2c3

This isn't what I'm really after. At some point I might want to 
implement the interface partially.

interface A { ... }
class B : A {
    A a;
    // implementation of A goes here, but I'd like it to just 
redirect to a for all that I do not explicitly implement //
}

There seems to be some cool stuff that Kenji has used that I was 
not familiar with. I'm not quite sure if it does exactly what I'm 
asking but it looks close.