Value of type 'String' has no member 'characterAtIndex'

Question

I'm using the following UITextFieldDelegate method:

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange,
replacementString string: String) -> Bool {

and get the error-message above when trying to access the first character:

let firstChar = string.characterAtIndex(0)

I don't know what's wrong with this code, since the NSString class reference lists the function:

func characterAtIndex(_ index: Int) -> unichar

Do you know what I am doing wrong?

Answer 1

You have to explicitly bridge (cast) String to NSString:

(string as NSString).characterAtIndex(0)

Answer 2

Although Swift's String and NSString are interchangeable, in the sense that you can pass String to APIs expecting NSString and vice versa, the two are not the same. Generally, you cannot call NSString methods on String without a cast.

The way you get the initial character from String is different - rather than using characterAtIndex(0) you call

let str = "Hello"
let initialChar = str[str.startIndex] // will throw when str is empty

or

let initialChar = str.characters.first // produces an optional value