为什么这个标签没有显示正确的值？ Swift

Question

我编写了一个代码来从我的 CoreDate 实体中获取数据，以将最高整数显示为 Highscore 标签中的值。我不明白为什么它不起作用？我试过带或不带额外功能...

func loadHighscore() {
        
        //Kontext identifizieren
        guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {
            return
        }
        
        //Anfrage stellen
        let context = appDelegate.persistentContainer.viewContext
        let entityName = "PushUps"
        
        let request = NSFetchRequest<NSFetchRequestResult>(entityName: entityName)
        
        do {
            let results = try context.fetch(request)
            for result in results {
            
                guard let count = (result as! NSManagedObject).value(forKey: "highScore") as? Int16 else {
                        return
        
                    }
            }
                if count > highScore {
                    highscoreLabel.text = "Highscore: \(count)"
                    highScoreChanged(newHighScore: Int16(count))
                    // Console statement:
                    print("New Highscore: \(count)")
                }
            } catch {
                print("error")
            }
        
    }
    
    
    func highScoreChanged(newHighScore: Int16) {
        highscoreLabel.text = "Highscore: \(newHighScore)"
    }
    
    
    
    
}

Answer 1

务必在主队列中执行标签更新。否则可能无法完成。

Answer 2

你的做法有点奇怪

更好的方法是加载按 highScore 降序排列的数据，因此第一项是具有最高值的项。

强烈建议利用通用核心数据类型并使用点符号而不是 KVC value(forKey

func loadHighscore() {
    
    //Kontext identifizieren
    // delegate can be forced unwrapped. The app doesn't even launch if AppDelegate doesn't exist
    let appDelegate = UIApplication.shared.delegate as! AppDelegate
    
    //Anfrage stellen
    let context = appDelegate.persistentContainer.viewContext
    let entityName = "PushUps"
    
    // Use a specific fetch request
    let request = NSFetchRequest<PushUps>(entityName: entityName)
    // add a sort descriptor to sort the items by highScore descending
    request.sortDescriptors = [NSSortDescriptor(key: "highScore", ascending: false)]
    
    do {
        // results is an array of PushUps instances, no type cast needed
        let results = try context.fetch(request)
        if let result = results.first, result.highScore > highScore {
            highScore = result.highScore
            print("New Highscore: \(highScore)")
        } 
    } catch {
        print(error)
    }
    highscoreLabel.text = "Highscore: \(highScore)"
}

函数highScoreChanged也不需要。如果保存的高分高于当前值 (属性 highScore)，则更新属性，并在方法结束时使用 [=24] 的值更新文本字段=] highScore.

为什么这个标签没有显示正确的值？ Swift

Why is this Label not showing the correct value? Swift

label

function

swift