Swift - Custom Type Extensions


In Swift, you can extend existing types and add methods and computed properties.

This is the general preferred way to add new functionality to a class, rather than inheritance.

You can add functionality to exising class.

Or you want to divide its functionality into different sections for readability.

In Swift, you can extend any type: your own type and built-in types.

To create an extension, you use the extension keyword, followed by the name of the type you want to extend.

Once you extend a type, the methods and properties you defined in the extension are available to every instance of that type.

For example, to add methods and properties to the built-in Int type, you can do this:


extension Int { 
    var double  : Int { 
        return self * 2 
    } //www .j av a 2 s  .c o  m
    func multiplyWith(anotherNumber: Int) -> Int { 
        return self * anotherNumber 

print(2.double) // 4 
print(2.multiplyWith(anotherNumber: 5)) // 10


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