Static/dynamic dispatch

static.swift

struct Dog : Animal {
    func eat() {
        print("dog eats")
    }
    func talk() {
        print("dog talk")
    }
}

protocol Animal {
    func talk()
}

extension Animal {
    func eat() {
        print("animal eats")
    }
    func talk() {
        print("animal talk")
    }
}

func animalDoAnimalStuff(animal : Animal) {
    animal.eat()
    // eat is defined in extension, thus it is statically dispatched and will print "animal eats"

    animal.talk()
    // talk is declared in the protocol, thus it is dynamically dispatched and will print "dog talk"
}

let dog = Dog()
animalDoAnimalStuff(animal: dog)