How to add a character at a particular index in string in Swift

Swift 3

Use the native Swift approach:

var welcome = "hello"welcome.insert("!", at: welcome.endIndex) // prints hello!welcome.insert("!", at: welcome.startIndex) // prints !hellowelcome.insert("!", at: welcome.index(before: welcome.endIndex)) // prints hell!owelcome.insert("!", at: welcome.index(after: welcome.startIndex)) // prints h!ellowelcome.insert("!", at: welcome.index(welcome.startIndex, offsetBy: 3)) // prints hel!lo

If you are interested in learning more about Strings and performance, take a look at @Thomas Deniau's answer down below.

If you are declaring it as NSMutableString then it is possible and you can do it this way:

let str: NSMutableString = "3022513240)"str.insert("(", at: 0)print(str)

The output is :

(3022513240)

EDIT:

If you want to add at starting:

var str = "3022513240)"str.insert("(", at: str.startIndex)

If you want to add character at last index:

str.insert("(", at: str.endIndex)

And if you want to add at specific index:

str.insert("(", at: str.index(str.startIndex, offsetBy: 2))

var myString = "hell"let index = 4let character = "o" as CharactermyString.insert(    character, at:    myString.index(myString.startIndex, offsetBy: index))print(myString) // "hello"

Careful: make sure that index is smaller than or equal to the size of the string, otherwise you'll get a crash.