Swift program to create a subscript with the read-only property

Program/Source Code:

The source code to create a subscript with read-only property is given below. The given program is compiled and executed successfully.

// Swift program to create a subscript 
// with the read-only property

import Swift

struct Colors {
    private var colors = ["Red", "Green", "Blue", "White","Black"]
    subscript(index: Int) -> String {
        get {
            return colors[index]
        }
    }
}

var Col = Colors()
// Col[3] = "Yellow" //this statement will generate error.

print(Col[0])
print(Col[1])
print(Col[2])
print(Col[3])
print(Col[4])

Output:

Red
Green
Blue
White
Black

...Program finished with exit code 0
Press ENTER to exit console.

Explanation:

In the above program, we imported a package Swift to use the print() function using the below statement,

import Swift

Here, we created a structure Colors that contains an array of strings colors.  In the Colors structure, we defined a read-only property using the subscript keyword to get the value of the colors array based on the index. Then we created a structure variable Col. After that, we printed the values of the colors array based on the index.