Re: Array of objects and their inheritance
Thank you for the explanation
Re: Array of objects and their inheritance
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.
Array of objects and their inheritance
Hi.
I'm having a hard time understanding D's inheritance. Consider
the following code:
class Parent {
public int x = 10;
}
class Child : Parent {
public int y = 20;
}
void main() {
import std.stdio;
Parent[] array;
auto obj1 = new Parent();
auto obj2 = new Child();
array ~= obj1;
array ~= obj2;
writeln(array[0]); // prints Parent, as expected
writeln(array[1]); // prints Child, so I assume that if
it's a Child, we can access Child's fields
writeln(array[0].x); // 10
writeln(array[1].y); // Error: no property 'y' for type
'Parent'
}
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'?
Well, if it's still a 'Child', why we can't access it's fields?
And what is the proper way of storing a collection of inherited
objects without losing access to their fields and methods?
Please point me in the right direction. I'm (still) relatively
new to D, and will appreciate any help.
