Delegating constructors

[FMorschel]

Today on the collection package we need a DelegatingList<E> class. All it does is receive a list and, as the name suggests, delegate all calls to methods, getters, setters and such to that specific list.

This week I had the same problem/need but with a FocusNode class. And I had to delegate 48 getters and setters to a base FocusNode. I'd like to propose a delegating constructor of sorts.

I imagine the syntax to be something like:

class A extends FocusNode {
  A(FocusNode f) : super = f;
}

[lrhn]

The thing you need is the ability to forward members of an interface to a specific object.

Consider something like:

class A implements FocusNode as _f {
  final FocusNode _f;
  A(this._f);
}

or

class A implements FocusNode{
  delegate FocusNode _f;
  final FocusNode _f;
  A(this._f);
}

or something similar, where a class defines that every method of an interface that it doesn't explicitly implement, is forwarded to an object which implements that interface.

I'm sure we have an issue for that already, but GitHub search being what it is, I haven't found it yet.

[FMorschel]

I think, I found what you were talking about #3748 (which being in the SDK could be why you didn't find it). I found the mention on #418 (comment) which is similar but I don't think this is the exact thing.

Should I move this discussion to one of those issues if they're what you were thinking?

[lrhn]

I moved (now numbered) #3748 into the language repo, so let's defer to that.