「不能增加endIndex的」 - 錯誤的原因的UITextView

Question

表情符的我有延長UITextView：

extension UITextView { 

    func separatedWordsInFrontCursor(infront: Bool = true) -> [String] { 

     let cursorPosition = selectedRange.location 
     let separationCharacters = NSCharacterSet(charactersInString: " ") 

     let beginRange = Range(start: text.startIndex.advancedBy(0), end: text.startIndex.advancedBy(cursorPosition)) 
     //fatal error: can not increment endIndex 

     let endRange = Range(start: text.startIndex.advancedBy(cursorPosition), end: text.startIndex.advancedBy(text.characters.count)) 

     let beginPhrase = text.substringWithRange(beginRange) 
     let endPhrase = text.substringWithRange(endRange) 

     return infront ? beginPhrase.componentsSeparatedByCharactersInSet(separationCharacters) : endPhrase.componentsSeparatedByCharactersInSet(separationCharacters) 
    } 
} 

錯誤是如下：

fatal error: can not increment endIndex

這是我嘗試鍵入到UITextView：

UITextView的鍵盤類型設置爲Default。

當錯誤出現：

cursorPosition is 3 
text.characters.count is 2 
text.startIndex is 0 
text.startIndex.advancedBy(2) is 3 
text.startIndex.advancedBy(cursorPosition) is "fatal error: can not increment endIndex" 

我怎樣才能解決這個？

Answer 1

正如@馬丁r表示，我們需要對NSRange和NSString操作，所以該溶液以下：

private func separatedWordsInFrontCursor(infront: Bool = true) -> [String] { 

    let cursorPosition = selectedRange.location 
    let separationCharacters = NSCharacterSet(charactersInString: " ") 

    let nstext = NSString(string: text) 

    let beginRange = NSRange(location: 0, length: cursorPosition) 
    let endRange = NSRange(location: cursorPosition, length: nstext.length - cursorPosition) 

    let beginPhrase = nstext.substringWithRange(beginRange) 
    let endPhrase = nstext.substringWithRange(endRange) 

    return infront ? beginPhrase.componentsSeparatedByCharactersInSet(separationCharacters) : endPhrase.componentsSeparatedByCharactersInSet(separationCharacters) 
}