Subscripts

Hello,

Subscripts are a shortcut to access member items of a collection, list, or directory.

Use subscripts to set and retrieve values ​​according to the index without the need for separate getter and setter methods.

// The use of arrays in literal form is an example of subscripts.

var swiftArray = [ "Apple" , "Google" , "Amazon" , "Microsoft" ] 
swiftArray [ 2 ] = "IBM" 
print(swiftArray)

//replaced Amazon with IBM at index 2. index in array start from 0.

Subscript can be defined for classes, structs, and enums.

Subscripts are used to access the elements of a collection-type object. We can use subscripts to get and get according to the index.

So we don't need extra methods.

For example, we can access the elements of an array with someArray [index] or the element of a dictionary with someDictionary [key].

We are making these uses all the time actually, these are subscripts written for Swift.

We can define more than one subscript for a type.

The appropriate subscript will be selected according to the type of index that we have inserted in the subscript (it will be overloaded).

Subscripts are not limited to one dimension. Thus, we can define multiple input parameters specific to the needs of the type used for a subscript.

Subscripts allow us to query an instance (with arguments that we will insert in the brackets after the name).

// In this example instance in subscription is called
instance[1]

How to Write a Subscript?

First of all, we write the subscript keyword. Then we define it as one or more parameters and write the return type.

This is the same method as we know the syntax. However, unlike the instance method, subscripts are read-write or read-only.

This behavior is passed by getter and setter to computed properties in the same way:

// subscript keyword has been defined
// one index was passed as parameter
subscript(index: Int) -> Int {
    get {
        // Return an appropriate subscript value here.
    }
 set(newValue) {
        // Perform a suitable setting action here.
    }
}

As with read-only computed properties, we can define a read-only subscript by removing the get keyword and parentheses.

Congratulations 🎉

In this lesson, we have learned Subscripts on Swift.

See you in the next lesson.