Swift String Extensions

One of the great things about Swift for iOS / tvOS development is how the language can be extended.

Here are some useful string extensions for Swift:

extension String {
    var length : Int {
        return self.characters.count

    subscript(integerIndex: Int) -> Character {
        let index = startIndex.advancedBy(integerIndex)
        return self[index]
    subscript(integerRange: Range<Int>) -> String {
        let start = startIndex.advancedBy(integerRange.startIndex)
        let end = startIndex.advancedBy(integerRange.endIndex)
        let range = start..<end
        return self[range]

    var localized: String {
        return NSLocalizedString(self, tableName: nil, bundle: NSBundle.mainBundle(), value: "", comment: "")

Add this code to a file such as StringExtension.swift and you're good to go.

String Length

As its name implies, you can determine the length of a string in a much simpler way:

let myStr = "Hello"
print("The string \(myStr) has \(myStr.length) characters")

Single Character

You can retrieve a single character from a string using an integer subscript:

let myStr = "Hello"
let first = myStr[0]

print("The first character of \(myStr) is \(first)")


You can retrieve a substring using an integer range:

let myStr = "Goodbye"
let good = myStr[0 ... 3]
let bye = myStr[4 ..< 7]

Localised String

It's best practice to not hard-code any string that is displayed in your code. Instead, strings should be kept in a strings file (such as Localizable.strings, of which there would be one such file for each translated language).

A single entry in the strings file may look as follows:

"HelloMessage" = "Hello";

Using the .localized extension above, you can bring in the translated string as follows:

let translatedHello = "HelloMessage".localized
print("The translated version is \(translatedHello)")

Do you have any other useful string extensions? Email us: hello@crunchybagel.com.