Swift: Developing iOS Applications

Read and write custom subscripts

Let's see how to define a subscript that is used to read and write to a backend array. Reading and writing to a backend storage class is one of the most common uses of custom subscripts, but, as we will see in this chapter, we do not need to have a backend storage class. The following code is a subscript to read and write an array:

class MyNames {
    private var names:[String] = ["Jon", "Kim", "Kailey", "Kara"]
    subscript(index: Int) -> String {
        get {
            return names[index]
        }
        set {
            names[index] = newValue
        }
    }
}

As we can see, the syntax is similar to how we can define properties within a class using the get and set keywords. The difference is that we declare the subscript using the subscript keyword. We then specify one ...