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

Question

I have a string like this in Swift:

var stringts:String = \"3022513240\"

If I want to change it to string to something like this: \"(

Answer 1

Swift 4.2 version of Dilmurat's answer (with code fixes)

extension String {
    mutating func insert(string:String,ind:Int) {
        self.insert(contentsOf: string, at:self.index(self.startIndex, offsetBy: ind) )
    }
}

Notice if you will that the index must be against the string you are inserting into (self) and not the string you are providing.

Answer 2

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))

Answer 3

var phone= "+9945555555"

var indx = phone.index(phone.startIndex,offsetBy: 4)

phone.insert("-", at: indx)

index = phone.index(phone.startIndex, offsetBy: 7)

phone.insert("-", at: indx)

//+994-55-55555

Answer 4

Swift 3

Use the native Swift approach:

var welcome = "hello"

welcome.insert("!", at: welcome.endIndex) // prints hello!
welcome.insert("!", at: welcome.startIndex) // prints !hello
welcome.insert("!", at: welcome.index(before: welcome.endIndex)) // prints hell!o
welcome.insert("!", at: welcome.index(after: welcome.startIndex)) // prints h!ello
welcome.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.

Answer 5

Maybe this extension for Swift 4 will help:

extension String {
  mutating func insert(string:String,ind:Int) {
    self.insert(contentsOf: string, at:self.index(self.startIndex, offsetBy: ind) )
  }
}

Answer 6

You can't use in below Swift 2.0 because String stopped being a collection in Swift 2.0. but in Swift 3 / 4 is no longer necessary now that String is a Collection again. Use native approach of String,Collection.

var stringts:String = "3022513240"
let indexItem = stringts.index(stringts.endIndex, offsetBy: 0)
stringts.insert("0", at: indexItem)
print(stringts) // 30225132400