xcode Swift 4 - 表达式类型'@lvalue String?' 在没有更多上下文的情况下是模棱两可的
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/52655459/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Swift 4 - Expression type '@lvalue String?' is ambiguous without more context
提问by Jose Fermin
I'm trying to record a score and Highscore on a game that I'm doing. But I've been getting this error:
我正在尝试记录我正在做的游戏的分数和高分。但我一直收到这个错误：
Any clues of how can I fix this? I have Xcode 10 and I'm working with Swift 4. Thanks in advance!
我该如何解决这个问题的任何线索？我有 Xcode 10，我正在使用 Swift 4。提前致谢！
import UIKit
import Foundation
class ScoreVC: UIViewController {
@IBOutlet weak var scoreLabel: UILabel!
@IBOutlet weak var highscoreLabel: UILabel!
@IBOutlet weak var reset: UIButton!
@IBOutlet weak var points: UIButton!
var Score = 0
var Highscore = 0
override func viewDidLoad() {
super.viewDidLoad()
let HighscoreDefault = UserDefaults.standard
if (HighscoreDefault.value(forKey: "Highscore") != nil) {
Highscore = HighscoreDefault.value(forKey: "Highscore") as! Int
highscoreLabel.text = NSString(format: "Highscore: %i", Highscore) as String
}
}
@IBAction func resetButton(_ sender: Any) {
Score = 0
scoreLabel.text = NSString(format: "Score: %i", Score) as String
}
@IBAction func pointsButton(_ sender: Any) {
Score +=
scoreLabel.text = NSString(format: "Score: %i", Score) as String
if (Score > Highscore) {
Highscore = Score
highscoreLabel.text = NSString(format: "Highscore: %i", Highscore) as String
var HighscoreDefault = UserDefaults.standard
HighscoreDefault.setValue(Highscore, forKey: "Highscore")
HighscoreDefault.synchronize()
}
}
}
回答by Hemraj Jhariya
Edit this line from pointsButton :
从 pointsButton 编辑此行：
guard let scoreLabel = scoreLabel.text else {
return
}
回答by ielyamani
Edit this line from pointsButton:
编辑此行pointsButton：
Score += 1
As to the error message,
至于错误信息，
scoreLabel.text = NSString(format: "Score: %i", Score) as String
Here scoreLabel.textis an lvaluesince it exists on the left of the assignment operator =. In the line before, in your original code, Score +=was expecting an rvalueand the assignment operation can't be treated as an rvalue.
这scoreLabel.text是一个左值，因为它存在于赋值运算符的左侧=。在之前的行中，在您的原始代码中，需要Score +=一个右值，并且不能将赋值操作视为右值。
