Re: Covariant callback functions, or assigning base class members through a subclass reference

[Jacob Carlborg via Digitalmars-d-learn]

On 2015-07-14 17:28, Rene Zwanenburg wrote:

Given the following code:

class Base
{
     alias CallbackType = void delegate(Base);

     CallbackType callback;

     void foo()
     {
         callback(this);
     }
}

class Derived : Base
{

}

void main()
{
     auto d = new Derived();
     d.callback = (Derived d) { /* Do something */ }
}

Obviously this won't compile, since the callback function needs to have
Base as parameter, not Derived.

You can cast the delegate. It's probably unsafe but a simple example works.

--
/Jacob Carlborg