Delegate Protocol Swift

GameScene.swift

import Foundation
import SpriteKit

class GameScene : SKScene, PlayerControllerDelegate
{
	// MARK:- PROPERTIES

	var playerController : PlayerController = PlayerController()

	// MARK:- INIT

	override func didMove(to view: SKView)
    {
        self.playerController.delegate = self
    }

 	// MARK:- DELEGATE FUNCTIONS

    func playerDidAttack()
    {
    	print("player did attack")
    }
}

Player.swift

import SpriteKit

class Player : SKSpriteNode
{
	func attack() 
 	{
		print("player attacks")
	}
}

PlayerController.swift

import Foundation

class PlayerController : NSObject
{
	var player : Player = Player() // create player object
	var delegate : PlayerControllerDelegate? // create delegate object

	func attackKeyPressed()
	{
		player.attack() // tell player object to attack
		delegate?.playerDidAttack // tell delegate to tell scene to run playerDidAttack
	}
}

protocol PlayerControllerDelegate
{
    func playerDidAttack()
}