first example, animals 25.01.18

class Animal
{
    var name:String
    var isAlive:Bool

    init(name:String) {
        self.name=name
        self.isAlive=true
    }

    func makeSound()
    {
        print("Animal is making a sound ...")
    }
}


class Lion:Animal
{
    func eat(cow:Cow) {
        if (self.isAlive)
        {
            if (cow.isAlive)
            {
                print("Lion \(self.name) is eating cow \(cow.name)")
                cow.isAlive=false
            }
            else
            {
                print("Lion \(self.name) cann't eat a dead cow \(cow.name)")
            }
        }
        else
        {
                print("dead Lion \(self.name) cann't eat a cow \(cow.name)")
        }

    }

    override func makeSound()
    {
        print("Lion is making a sound ...")
    }
}



class Cat:Animal
{
    func eat(mouse:Mouse) {
        if (self.isAlive)
        {
            if (mouse.isAlive)
            {
                print("Cat \(self.name) is eating mouse \(mouse.name)")
                mouse.isAlive=false
            }
            else
            {
                print("Cat \(self.name) cann't eat a dead mouse \(mouse.name)")
            }
        }
        else
        {
                print("Dead Cat \(self.name) cann't eat a mouse \(mouse.name)")
        }

    }

    func drinkMilk(cow:Cow) {
        if (self.isAlive)
        {
            if (cow.isAlive)
            {
                print("Cat \(self.name) is drinking milk from cow \(cow.name)")
            }
            else
            {
                print("Cat \(self.name) cann't get milk from a dead cow \(cow.name)")
            }
        }
        else
        {
                print("Dead cat \(self.name) cann't drink milk from cow \(cow.name)")
        }

    }

    override func makeSound()
    {
        print("Cat is making a sound ...")
    }
}

class Cow:Animal
{
    func canGiveMilk() -> Bool
    {
        return self.isAlive
    }

    override func makeSound()
    {
        print("Cow is making a sound ...")
    }
}

class Mouse:Animal
{
    override func makeSound()
    {
        print("Mouse is making a sound ...")
    }
}
var lion:Lion=Lion(name:"myLion")
var cow:Cow=Cow(name:"myCow")
var cat:Cat=Cat(name:"myCat")

lion.makeSound()
cow.makeSound()
cat.makeSound()

cat.drinkMilk(cow:cow)
lion.eat(cow:cow)
lion.eat(cow:cow)
cat.drinkMilk(cow:cow)