ios - 刚刚升级到 Xcode 8.3，现在出现错误 : "Type GameScene has no member: updateCounting"

Question

我的代码一直在运行并正常运行，直到我最近更新到 Xcode 8.3。现在我的代码无法运行，出现错误:“Type GameScene has no member: updateCounting”。我读过类似的问题和解决方案，但没有一个能够帮助解决问题。我仍在快速学习，因此任何帮助将不胜感激。

这是我的代码:

    let highScoreDefault = UserDefaults.standard
    highScore = highScoreDefault.integer(forKey: "Highscore")
    highScoreLabel.text = "\(highScore)"

func scoreUpdate(_ currentTime: CFTimeInterval){

    if (score > highScore) {
        highScore = score
        highScoreLabel.text = NSString(format: "Highscore : %i", highScore) as String

        let highscoreDefault = UserDefaults.standard
        highscoreDefault.setValue(highScore, forKey: "Highscore")
        highscoreDefault.synchronize()

    }

    }

func updateCounting() {
        scoreLabel.text = String(self.score)
        finalScore.text = String(self.score)

        let highScoreDefault = UserDefaults.standard
        highScore = highScoreDefault.integer(forKey: " ")
        highScoreLabel.text = "\(highScore)"

    if (score > highScore) {
        highScore = score
        highScoreLabel.text = NSString(format: " %i", highScore) as String

        let highscoreDefault = UserDefaults.standard
        highscoreDefault.setValue(highScore, forKey: " ")
        highscoreDefault.synchronize()
    }

        self.score += 1
        print(score, terminator: " ")

    }

        timer = Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: #selector(GameScene.updateCounting), userInfo: nil, repeats: true)

         // The above line of code is what's giving the error

        totalCoins = UserDefaults.standard.integer(forKey: "Total Coins")
        totalCoinLabel.text = "\(totalCoins)"

Answer 1

建议的解决方案

尝试在函数名称前添加 @objc，如下所示:

@objc func updateCounting() {
    // function code here
}

然后使用#selector(self.updateCounting)

工作示例

我采用了您的代码并对其进行了大幅简化。我从一个新的单一 View 项目开始。我添加了 GameScene.swift 文件并修改了 ViewController 类。请参阅下面的代码。运行项目，你会看到日志显示:

Updating count: 0 
Updating count: 1 
Updating count: 2 
Updating count: 3

GameScene.swift

import Foundation

class GameScene {
    var timer: Timer = Timer()
    var counter: Int = 0        

    @objc func updateCounting(){
        print("Updating count: \(counter)")
        counter += 1
    }

    func updateTimer() {
        timer = Timer.scheduledTimer(timeInterval: 0.5, target: self, selector: #selector(updateCounting), userInfo: nil, repeats: true)
    }
}

ViewController.swift

import UIKit

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        let game = GameScene()
        game.updateTimer()
    }
}

Github 链接: https://github.com/starkindustries/TimerTestProject

有效的语法选项

以下选项在此示例项目中测试成功:

1. 选择器:#selector(updateCounting)
2. 选择器:#selector(self.updateCounting)
3. 选择器:#selector(GameScene.updateCounting)

假设您想向 updateCounting 函数添加一个参数。将 updateCounting 方法名称更改为 @objc func updateCounting(_ timer: Timer) 并将选择器更改为 selector: #selector(updateCounting(_:)

语法讨论

一旦我删除@objc，编译器就会显示此错误:

Argument of '#selector' refers to instance method 'updateCounting' that is not exposed to Objective-C

另一个答案中的评论之一也暗示了这一点:

I needed to add write the target function like this: @objc func updateTime() {} Timer.scheduledTimer swift 3 pre iOS 10 compatibility

Apple 文档指出:

The selector should have the following signature: timer​Fire​Method:​ (including a colon to indicate that the method takes an argument). The timer passes itself as the argument, thus the method would adopt the following pattern: - (void)timerFireMethod:(NSTimer *)timer https://developer.apple.com/reference/foundation/timer/1412416-scheduledtimer

即使我使用的是 Swift 版本的文档，它也显示了 Objective C 版本的timerFireMethod。因此，也许 Timer 类需要一个 Objective C 选择器，就像所提示的编译器错误一样。然而，文档指出该方法应该有一个参数(计时器)，但我只是使用不带参数的函数成功测试了它。