We can also make the subscript read-only by either not declaring a setter method within the subscript or by not implicitly declaring a getter or setter method. The following is the first example that shows how to declare read-only subscripts:

//No getter/setters implicitly declared
subscript(index: Int) ->String {
  return names[index]
}

The following is the second example:

//Declaring only a getter
subscript(index: Int) ->String {
  get {
    return names[index]
  }
}

In the first example, we do not define either a getter or setter method. So, Swift sets the subscript as read only and the code acts as if it was in a getter definition. In the second example, we specifically set the code in a getter definition. Both examples are valid read-only subscripts.