static data in a sub-class

[Ali Çehreli]

On 12/22/2012 12:44 PM, Steve D wrote:
> Hello,
> How can I get class B's array printed, using inherited A's function?
> (Dmd 2.060)
>
> class A {
> static float[3] hi = 1;
>
> void f() { writefln("hi %s",hi); }
> }
>
> class B : A {
> static float[3] hi = 2;
> }
>
> B b = new B();
> b.f(); // prints 'hi [1,1,1]'
> // can I get it to use B's overridden hi: [2,2,2] ?
>
> Thanks for your help :)
> Steve

One way is to present the data to the superclass during construction:

import std.stdio;

class A {
     const float[] hi;

     this(float[] hi) {
         this.hi = hi;
     }

     void f() { writefln("hi %s",hi); }
}

class B : A {
     static float[3] hi = 2;

     this() {
         super(hi);
     }
}

void main()
{
     B b = new B();
     b.f();
}

Another ways is for A to require that the subclasses present the data by 
a member function:

import std.stdio;

class A {
     abstract float[] hi_data();

     void f() { writefln("hi %s", hi_data()); }
}

class B : A {
     static float[3] hi = 2;

     override float[] hi_data() {
         return hi;
     }
}

void main()
{
     B b = new B();
     b.f();
}

Orthogonally, if f() is strictly on the A interface, then you can make 
it a final function:

     final void f() { writefln("hi %s", hi_data()); }

Ali