- Converts the interface of a class into another interface the clients expect.
We have two protocols which are Turkey and Duck. Both of them can fly (with different distances) but one gobbles and the other one quacks.
protocol Turkey {
func gobble()
func fly()
}
protocol Duck {
func quack()
func fly()
}Now we will create a class WildTurkey.
class WildTurkey: Turkey {
func gobble() {
print("Gobble gooble")
}
func fly() {
print("I'm flying short distance.")
}
}And a class for MallardDuck.
class MallardDuck: Duck {
func quack() {
print("Quack.")
}
func fly() {
print("I'm flying.")
}
}The below class makes all the ducks quack and fly. But we should create an adapter to make a turkey gobble and fly with them.
class DuckSimulator {
var ducks = [Duck]()
func addDuck(duck: Duck) {
ducks.append(duck)
}
func flyAll() {
for duck in ducks {
duck.fly()
}
}
func quackAll() {
for duck in ducks {
duck.quack()
}
}
}The TurkeyAdapter class applies Duck protocol and we define an instance of Turkey. The protocol provides a quack method in which we will execute the turkey's gobble method and a fly method to execute the turkey's fly method. So we adapt Turkey to Duck.
class TurkeyAdapter: Duck {
var turkey: Turkey
init(turkey: Turkey) {
self.turkey = turkey
}
func quack() {
turkey.gobble()
}
func fly() {
turkey.fly()
}
}Now we can test it.
var duckSimulator = DuckSimulator()
duckSimulator.addDuck(duck: MallardDuck())
duckSimulator.addDuck(duck: MallardDuck())
duckSimulator.addDuck(duck: TurkeyAdapter(turkey: WildTurkey()))
duckSimulator.flyAll()
// I'm flying.
// I'm flying.
// I'm flying short distance.
duckSimulator.quackAll()
// Quack.
// Quack.
// Gobble gooble