Using stringByReplacingCharactersInRange in Swift
swift
Solution
Here's how to calculate the resulting string in various Swift versions.
Note that all methods use `-[NSString stringByReplacingOccurrencesOfString:withString:]` in exactly the same way, just differing in syntax.
This is the preferred way to calculate the resulting string. Converting to a Swift `Range` and use that on a Swift `String` is error prone. Johan's answer for example is incorrect in a couple of ways when operating on non-ASCII strings.
Swift 3:
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
let result = (textField.text as NSString?)?.replacingCharacters(in: range, with: string) ?? string
// ... do something with `result`
}
Swift 2.1:
func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
let result = (textField.text as NSString?)?.stringByReplacingCharactersInRange(range, withString: string)
// ... do something with `result`
}
Swift 1 (only left here for reference):
let result = textField.text.bridgeToObjectiveC().stringByReplacingCharactersInRange(range, withString:string)
Problem
I'm trying to use UITextFieldDelegate in Swift/Xcode6 and I'm struggling with the way I'm supposed to use stringByReplacingCharactersInRange. The compiler error is 'Cannot convert the expression's type 'String' to type '$T8'. ``` func textField(textField: UITextField!, shouldChangeCharactersInRange range: NSRange, replacementString string: String!) -> Bool { let s = textField.text.stringByReplacingCharactersInRange(range:range, withString:string) if countElements(s) > 0 { } else { } return true } ``` Update for Xcode 6 Beta 5: The thing is shouldChangeCharactersInRange gives an NSRange object and we'd need a Swift Range object for stringByReplacingCharactersInRange. Can this still be considered a bug as I don't see why we should still be dealing with NS* objects? The String argument of the delegate method is anyway of a Swift type.