Re: 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