如何将NSRange转换为Range<String。索引>在Swift?
我想使用以下UITextFieldDelegate方法:
func textField(textField: UITextField!,
shouldChangeCharactersInRange range: NSRange,
replacementString string: String!) -> Bool {
textField.text.stringByReplacingCharactersInRange(???, withString: string)
当前回答
在公认的答案中，我发现可选选项很麻烦。这适用于Swift 3，似乎对表情符号没有问题。
func textField(_ textField: UITextField,
shouldChangeCharactersIn range: NSRange,
replacementString string: String) -> Bool {
guard let value = textField.text else {return false} // there may be a reason for returning true in this case but I can't think of it
// now value is a String, not an optional String
let valueAfterChange = (value as NSString).replacingCharacters(in: range, with: string)
// valueAfterChange is a String, not an optional String
// now do whatever processing is required
return true // or false, as required
}
其他回答
我发现最干净的swift2唯一的解决方案是在NSRange上创建一个类别:
extension NSRange {
func stringRangeForText(string: String) -> Range<String.Index> {
let start = string.startIndex.advancedBy(self.location)
let end = start.advancedBy(self.length)
return Range<String.Index>(start: start, end: end)
}
}
然后调用它from for textfield delegate函数:
func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
let range = range.stringRangeForText(textField.text)
let output = textField.text.stringByReplacingCharactersInRange(range, withString: string)
// your code goes here....
return true
}
Swift 3.0 beta版官方文档在标题String下为这种情况提供了标准解决方案。UTF16View中的UTF16View元素匹配NSString字符标题
这与Emilie的回答相似，但是，因为你特别问如何将NSRange转换为Range<String。索引>，你会这样做:
func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
let start = advance(textField.text.startIndex, range.location)
let end = advance(start, range.length)
let swiftRange = Range<String.Index>(start: start, end: end)
...
}
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
guard let current = textField.text, let r = Range(range, in: current) else {
return false
}
let text = current.replacingCharacters(in: r, with: string)
// ...
return true
}
在Swift 2.0中假设func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: string) -> Bool {:
var oldString = textfield.text!
let newRange = oldString.startIndex.advancedBy(range.location)..<oldString.startIndex.advancedBy(range.location + range.length)
let newString = oldString.stringByReplacingCharactersInRange(newRange, withString: string)
