• slaid (27/27) Sep 01 2016 I have a snippet:
• Basile B. (49/52) Sep 01 2016 The field height is not overridden. In C you have two "height".
• slaid (2/14) Sep 01 2016 Just what I needed, thanks a bunch!

slaid <mhrawcliffe gmail.com> writes:

I have a snippet:

   import std.stdio;
   import std.algorithm;

   abstract class A {
       int height = 0;
   }

   class B : A {
   }

   class C : A {
       int height = 1;
   }

   void main() {
       A[][int] list;
       list[0] = new A[](0);
       list[0] ~= new B();
       list[0] ~= new C();
       list[0] ~= new B();
       writeln(list[0].map!(x=>x.height));
   }

The output of this is [0, 0, 0] when if height was overridden it 
should print [0, 1, 0]. This is a trivial case for simplicity of 
the question, but in my actual code, I am trying to use the 
height field for sorting the A[] list (or reducing with max to 
get the object with the max height), but since they're all 0, 
none of the sorting occurs.

How do I override this height field?

Thanks

Basile B. <b2.temp gmx.com> writes:

On Thursday, 1 September 2016 at 11:09:18 UTC, slaid wrote:
 I have a snippet:

 How do I override this height field?

 Thanks

The field height is not overridden. In C you have two "height". 
Since your array is of type A[], map takes A.height.

abstract class A
{
     int height = 0;
}

class B : A {}

class C : A
{
     int height = 1;
}

void main()
{
     writeln((new C).height); // prints 0, the height of C
     writeln((cast(A)(new C).height); // prints 1, the height of A
}

Only methods are virtual. To solve the problem you can create a 
virtual getter:

°°°°°°°°°°°°°°°°°°°°°°
abstract class A
{
     int height();
}

class B : A
{
     override int height(){return 0;}
}

class C : A
{
     override int height(){return 1;}
}
°°°°°°°°°°°°°°°°°°°°°°

But since height is only a field you can just use the same 
variable and set the value in the constructor (for example)

°°°°°°°°°°°°°°°°°°°°°°
abstract class A
{
     int height;
}

class B : A
{
     this(){height = 0;}
}

class C : A
{
     this(){height = 1;}
}
°°°°°°°°°°°°°°°°°°°°°°

slaid <mhrawcliffe gmail.com> writes:

On Thursday, 1 September 2016 at 11:34:28 UTC, Basile B. wrote:
 On Thursday, 1 September 2016 at 11:09:18 UTC, slaid wrote:
 I have a snippet:

 How do I override this height field?

 Thanks

 The field height is not overridden. In C you have two "height". 
 Since your array is of type A[], map takes A.height.

 Only methods are virtual. To solve the problem you can create a 
 virtual getter:

 But since height is only a field you can just use the same 
 variable and set the value in the constructor (for example)

Just what I needed, thanks a bunch!