SALE ENDS TODAY: Save 50% on all Swift books and bundles! >>

Extensions

Extensions allow you to add methods to existing types, to make them do things they weren’t originally designed to do.

For example, we could add an extension to the Int type so that it has a squared() method that returns the current number multiplied by itself:

extension Int {
    func squared() -> Int {
        return self * self
    }
}

To try that out, just create an integer and you’ll see it now has a squared() method:

let number = 8
number.squared()

Swift doesn’t let you add stored properties in extensions, so you must use computed properties instead. For example, we could add a new isEven computed property to integers that returns true if it holds an even number:

extension Int {
    var isEven: Bool {
        return self % 2 == 0
    }
}

SPONSORED Instabug helps you identify and resolve severe crashes quickly. You can retrace in-app events and know exactly which line of code caused the crash along with environment details, network logs, repro steps, and the session profiler. Ask more questions or keep users up-to-date with in-app replies straight from your dashboard. Instabug takes data privacy seriously, so no one sees your data but you! See more detailed features comparison and try Instabug's crash reporting SDK for free.

Save 50% on all books and bundles

The biggest ever Hacking with Swift sale is now on, letting you save 50% on all books and bundles. Learn something new with Swift and enjoy great savings while the sale lasts!

Click here to save 50% in our Black Friday sale!

BUY OUR BOOKS
Buy Pro Swift Buy Swift Design Patterns Buy Testing Swift Buy Hacking with iOS Buy Swift Coding Challenges Buy Swift on Sundays Volume One Buy Server-Side Swift (Vapor Edition) Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Advanced iOS Volume Three Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with macOS Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Server-Side Swift (Kitura Edition) Buy Beyond Code

Was this page useful? Let us know!

Average rating: 3.8/5