agilehands

struct AK47:Weapon{
	func fire(){
		print("Firing with AK47")
	}
}

agilehands

let player = Player()
player.currentWeapon = AK47()
player.currentWeapon?.fire() // prints "Firing with AK47"

agilehands

protocol Explosive{
  func detonate()
}

struct Grenade:Explosive{
  func detonate(){
    print("A grenade exploded!")
  }
}

agilehands

struct WeaponAdapterForExplosive:Weapon{
	var explosive:Explosive
	func fire(){
		self.explosive.detonate()
	}
}

player.currentWeapon = WeaponAdapterForExplosive(explosive:Grenade())
player.fire()

agilehands

// all implementation of Explosve that also implements Weapon, call `detonate` in `fire` method
extension Explosive where Self:Weapon{
	func fire(){
		self.detonate()
	}
}

// Finally, extend Grenade to Weapon
extension Grenade:Weapon{}

agilehands

// Entity One: Weapon
protocol Weapon{
	func fire(); // Weapon can be fire
}

// The Context: Player, who can fire a weapon
class Player{
	var currentWeapon:Weapon?;
		
	// Fire: call the `fire` method of the weapon