fataler Fehler: kann nicht erhöht endIndex

Question

Aus irgendeinem Grund bekomme ich

fatal error: can not increment endIndex

in Zeile myRange. Warum bekomme ich diesen Fehler? Ich verstehe nicht, was mit meinem Code falsch ist.

import UIKit 

class ViewController: UIViewController { 

@IBOutlet var drag: UIPanGestureRecognizer! 
@IBOutlet weak var currentLabel: UILabel! 
@IBOutlet weak var label1: UILabel! 
@IBOutlet weak var label2: UILabel! 
@IBOutlet weak var label3: UILabel! 
@IBOutlet weak var label4: UILabel! 
@IBOutlet weak var label5: UILabel! 
@IBOutlet weak var label6: UILabel! 
@IBOutlet weak var label7: UILabel! 
@IBOutlet weak var label8: UILabel! 
@IBOutlet weak var label9: UILabel! 

let letter = "OX" 
var currentLetter = Character!() 
var decide = 0 
var labelArray = [UILabel]() 
var moveCounter = 0 
override func viewDidLoad() { 
    super.viewDidLoad() 
    getCurrentLetter() 
    labelArray = [label1,label2,label3,label4,label5,label6,label7,label8,label9] 
} 

func getCurrentLetter() 
{ 
    let myRange = Range<String.Index>(start: letter.startIndex.advancedBy(decide), end: letter.startIndex.advancedBy(decide+1)) 
    currentLabel.text = letter.substringWithRange(myRange) 
    currentLetter = Character(letter.substringWithRange(myRange)) 
} 

func reset() { 
    decide = 0 
} 
@IBAction func dragObject(sender: UIPanGestureRecognizer) { 
    let points = sender.locationInView(view) 
    let currentPoints = currentLabel.frame.origin 
    currentLabel.center = CGPointMake(points.x, points.y) 
    for item in labelArray { 
     if CGRectContainsPoint(item.frame, points) { 
      item.text = String(currentLetter) 
      decide++ 
      drag.enabled = false 
      currentLabel.center = currentPoints 
     } else if drag.enabled == false { 
      decide++ 
      drag.enabled = true 
      currentLabel.center = currentPoints 
     } 
     if decide == 2 { 
      reset() 
     } 
     getCurrentLetter() 
     } 
    } 
} 

Answer 1

Ihr Problem ist, dass entweder decide oder decide+1 länger als die Zeichenfolge ist. Zum Glück gibt es einen eingebauten Code, um dies zu beheben.

Try

let myRange = Range<String.Index>(start: letter.startIndex.advancedBy(decide), end: letter.startIndex.advancedBy(decide+1)) 
currentLabel.text = letter.substringWithRange(myRange) 
currentLetter = Character(letter.substringWithRange(myRange)) 

mit

let end = letter.endIndex.advancedBy(-1, limit: letter.startIndex) //The -1 is actually required, as the 'limit:' bit does <=, not just < 
let pos = letter.startIndex.advancedBy(decide, limit: end) 
currentLetter = letter[pos] 
currentLabel.text = currentLetter