Array of objects and their inheritance

[Adam D. Ruppe via Digitalmars-d-learn]

On Thursday, 14 May 2015 at 19:00:16 UTC, tired_eyes wrote:
> First, I don't understand why we see array[2] as 'Child'. While 
> it is a 'Child', shouldn't it be shown as a 'Parent' due to we 
> explicitly create an array of 'Parents'?

It is getting the name through a virtual interface (a hidden one 
that has typeinfo).

class Base {
    string getName() { return "Base"; }
}

class Derived : Base {
    override string getName() { return "Derived"; }
}

Base b = new Derived();
b.getName() == "Derived"; // because the virtual function can 
still be called through an interface

> Well, if it's still a 'Child', why we can't access it's fields?

It is a Child object, but you are talking to it through the 
Parent interface, so only functions+members available on Parent 
can be accessed without casting it.

> And what is the proper way of storing a collection of inherited 
> objects without losing access to their fields and methods?

Best you can do is say

if(child = cast(Child) parentArray[0]) {
    // it is a child, now use child to access that
}


Though often a better way is to add an interface method that does 
it in the parent and is overridden in the child, just like with 
the getName above.