patterns/strategy/duck.d

module strategy.duck;
import strategy.flybehavior;
import strategy.quackbehavior;
import std.stdio : writeln;

abstract class Duck
{
    FlyBehavior flyBehavior;
    QuackBehavior quackBehavior;

    void display();

    void performFly()
    {
        flyBehavior.fly();
    }

    void performQuack()
    {
        quackBehavior.quack();
    }
    
    void swim()
    {
        writeln("All ducks float, even decoys!");
    }

    void setFlyBehavior(FlyBehavior fb)
    {
        flyBehavior = fb;
    }

    void setQuackBehavior(QuackBehavior qb)
    {
        quackBehavior = qb;
    }
}

class MallardDuck : Duck
{
    this()
    {
        quackBehavior = new Quack;
        flyBehavior = new FlyWithWings;
    }

    override void display()
    {
        writeln("I'm a real Mallard duck");
    }
}

class ModelDuck : Duck
{
    this()
    {
        quackBehavior = new Squeak;
        flyBehavior = new FlyNoWay;
    }

    override void display()
    {
        writeln("I'm a model duck");
    }
}