Default Implementation For an Interface

[Jacob Carlborg]

On 2012-02-16 20:05, Jonathan M Davis wrote:
> On Thursday, February 16, 2012 13:26:59 Jacob Carlborg wrote:
>> Since D have delegates I would use those for event handling and not
>> listeners. I think they are a much better fit, as long as you don't have
>> to force the user to handle many different events on the same object.
>
> Oh, I'm not necessarily arguing that using interfaces far listeners is the way
> to go (in fact, I agree that delegates would be much better). It's just that
> that's a prime example of a situation where you want default implementations
> for interface methods, since with single inheritance, you can't derive a class
> from multiple classes which give you default implementations for interface
> methods.

Ok, I see. I got the impression that you preferred listeners.

>>> Now, if you use template mixins, I believe that it's possible to use that
>>> to mixin default implementations for the functions in an interface, which
>>> should solve the problem for D. So, that's probably good enough for D
>>> without having to make it so that interface functions can have default
>>> implementations.
>>
>> Template mixins cause their own problems. You can't overload methods
>> with template mixins, may it's possible to get around that with aliases,
>> I don't remember.
>
> I thought that you could, since they can be virtual, unlike templated
> functions. I don't know though. It's not something that I've really had to
> worry about - particularly since so few of my D programs need classes, let
> alone interfaces (because most of my D programs are small).
>
> - Jonathan M Davis

Note that I'm saying "overload" not "override".

-- 
/Jacob Carlborg