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digitalmars.D.learn - Interface abstraction

reply "Frustrated" <c1514843 drdrb.com> writes:
If I use interfaces instead of classes is there a way to have new 
return the underlying interface that I want it to?


interface A { }
class B : A {}

auto a = new B; // should return cast(A)(new B);

Maybe it's not such a big deal though? (I can't think of any case 
where a being of type B will hurt since it is always implicitly 
castable to type A.
Dec 31 2013
parent reply "Adam D. Ruppe" <destructionator gmail.com> writes:
On Wednesday, 1 January 2014 at 00:31:03 UTC, Frustrated wrote:

 auto a = new B; // should return cast(A)(new B);


A a = new B;


 case where a being of type B will hurt since it is always 
 implicitly castable to type A.


Right, it'll always be usable anyway.
Dec 31 2013
parent reply "Frustrated" <c1514843 drdrb.com> writes:
On Wednesday, 1 January 2014 at 00:31:58 UTC, Adam D. Ruppe wrote:

 On Wednesday, 1 January 2014 at 00:31:03 UTC, Frustrated wrote:

 auto a = new B; // should return cast(A)(new B);


 A a = new B;


 case where a being of type B will hurt since it is always 
 implicitly castable to type A.


 Right, it'll always be usable anyway.


I guess I was thinking just for consistency since I'll always 
being trying to use interfaces instead of classes. I guess it's 
not a big deal though. In setting up little test units I'll end 
up using the classes and auto but probably not in the full 
project where I'll use factories and such.
Dec 31 2013
parent "Adam D. Ruppe" <destructionator gmail.com> writes:
On Wednesday, 1 January 2014 at 00:54:35 UTC, Frustrated wrote:

 not a big deal though. In setting up little test units I'll end 
 up using the classes and auto but probably not in the full 
 project where I'll use factories and such.


Yeah, if you use your own factory methods, you can always just 
have them return the interface.

Even as simple as:

InterfaceName make(Class, Args...)(Args args) { return new 
Class(args); }

which explicitly returns the interface, so if you did

auto a = make!Foo(10, 20); // a is typed to the interface
Dec 31 2013