Swift 4.2-类型'（____）->（）->（____）'的值没有成员'childNode'

Question

I created a custom class in swift to manage my main menu for a game I'm making I linked it to the SKScene file and tried to create a constant to access the variable and I got this error: Cannot use instance member 'childNode' within property initializer.

import SpriteKit
import GameplayKit

class MainMenu: SKScene {

    let startGameButton:SKSpriteNode = self.childNode(withName: "SpriteName")

    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {

    }
}

Does anyone know whats happening? If not is there another way to access sprites.

Answer 1

Initial values for let variables must be constants that can be initialized before the init() method is executed. That in turn means they can't reference self .

One workaround for that is making them lazy instance variables, which get initialized when they are first used (which, by definition, can't happen before init() has returned a reference to the object). In that case, the lazy variable would be initialized with the result from a closure.

Change:

let startGameButton:SKSpriteNode = self.childNode(withName: "SpriteName")

to

lazy var startGameButton:SKSpriteNode = self.childNode(withName: "SpriteName") as! SKSpriteNode