// constructor
public ModelDuck()
{
flyBehavior = new FlyNoWay(); // interface = class
quackBehavior = new Quack(); // interface = class
}
// constructor
public MallardDuck()
{
quackBehavior = new Quack(); // quackBehavior is a vairable from the base class. Quack is a concrete class (behavior) that implements the IQuackBehavior interface.
flyBehavior = new FlyWithWings(); // flyBehavior is a variable from the base class. FlyWithWings is a concrete class (behavior) that implements the IFlyBehavior interface.
}