import std;

​

interface Renderer {

}

​

void main()

{

    Renderer renderer;

​

    auto chip = new Chip();

​

    // Test Draw

    // 1. Init

    chip.draw(renderer);

    // 2. Hovered

    chip.to!(Chip.Hovered);

    chip.draw(renderer);

​

    // 3. Init

    chip.to!(Chip.Init);

    chip.draw(renderer);

    // 4. Hovered

    chip.to!(Chip.Hovered);

    chip.draw(renderer);

}

​

class Chip

{

    int state = 7;

    interface Behavior {

        void draw(Renderer renderer);

    }

    Behavior behavior;

    class Init : Behavior {

        void draw(Renderer renderer)

        {

            writeln("Chip.Init.draw(state=%s)".format(state));  

        }

    }

    class Hovered : Behavior {

        void draw(Renderer renderer)

        {

            writeln("Chip.Hovered.draw(state=%s)".format(state));

        }

    }

    this()

    {

        behavior = new this.Init();

    }

​

    void to(NewBehavior)()

    {

        behavior = new NewBehavior();

    }

​

    void draw( Renderer renderer )

    {

        behavior.draw(renderer);

    }

}

​