Re: passing subclass to superclass where parameter is a delegate for the superclass

[Alex via Digitalmars-d-learn]

On Wednesday, 14 November 2018 at 16:39:52 UTC, Alex wrote:

Are you looking for this?
https://dlang.org/phobos/std_traits.html#TransitiveBaseTypeTuple

It matches however not exactly your needs:

As all objects are derived from the Object class, you will always get it as the common parent. So... with the trait, you get a list but have still to make a decision which type to use.

Maybe, something like this:

´´´
import std.traits;

template properBase(T)
{
        static foreach(i, t; TransitiveBaseTypeTuple!A)
        {
                static if(hasMember!(t, "add_function")){}
                else
                {
                        static if(!__traits(compiles, {auto c = 
properBase.init;}))
                        {
                                alias properBase = 
TransitiveBaseTypeTuple!A[i-1];
                        }
                }
        }
}

void main(){}

class base
{
    void delegate(typeof(this)) stored_dg;
        this(){}
    void
    add_function (void delegate (typeof(this)) dlg)
    {
        stored_dg = dlg;
    }
}

class A : base
{
        alias pB = properBase!A;
    this ()
    {
        super ();
        add_function (&this.foo);
    }

    void foo (pB a)
    {
                import std.experimental.logger;
        log ("i got here");
    }
}
´´´