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)
NSString版本(相对于Swift String)的replacingCharacters(in: NSRange, with: NSString)接受NSRange,所以一个简单的解决方案是先将String转换为NSString。在Swift 3和2中,委托和替换方法的名称略有不同,所以这取决于你使用的Swift:
斯威夫特3.0
func textField(_ textField: UITextField,
shouldChangeCharactersIn range: NSRange,
replacementString string: String) -> Bool {
let nsString = textField.text as NSString?
let newString = nsString?.replacingCharacters(in: range, with: string)
}
快2.倍
func textField(textField: UITextField,
shouldChangeCharactersInRange range: NSRange,
replacementString string: String) -> Bool {
let nsString = textField.text as NSString?
let newString = nsString?.stringByReplacingCharactersInRange(range, withString: string)
}
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
}