Swift replace first character in string

Question

A very simple question, how do I replace the first character of a string. I'm probably doing something totally wrong, but I simply can't get it to work.

I have tried this: var query = url.query!.stringByReplacingOccurrencesOfString("&", withString: "?", options: NSStringCompareOptions.LiteralSearch, range: NSMakeRange(0, 1))

But it gives me the following error:

Cannot invoke 'stringByReplacingOccurrencesOfString' with an argument list of type '(String, withString: String, options: NSStringCompareOptions, range: NSRange)'

When I remove the NSMakeRange and change it to nil, it works, but it replaces all the &'s in the string.

Answer 1

Swift 4 or later

let string = "&whatever"
let output = "?" + string.dropFirst()

mutating the string

var string = "&whatever"
if !string.isEmpty {
    string.replaceSubrange(...string.startIndex, with: "?")
    print(string)  // "?whatever\n"
}

Answer 2

You can try this:

var s = "123456"

let s2 = s.replacingCharacters(in: ...s.startIndex, with: "a")

s2 // "a23456"