Notice: Undefined index: understanding-swift in /var/sites/hackingwithswift.com/site/src/Controller/NewBooksReadController.php on line 89
What the heck are closures and why does Swift love them so much? - a free tutorial

NEW: Subscribe to Hacking with Swift+ and accelerate your learning! >>

What the heck are closures and why does Swift love them so much?

Paul Hudson    @twostraws   

Go on, admit it: you asked yourself exactly this question. If you didn’t I’d be surprised, because closures are one of the most powerful features of Swift but also easily the feature that confuses people.

So, if you’re sitting here thinking “wow, closures are really hard”, don’t be dismayed – they are hard, and you finding them hard just means your brain is operating correctly.

One of the most common reasons for closures in Swift is to store functionality – to be able to say “here’s some work I want you to do at some point, but not necessarily now.” Some examples:

  1. Running some code after a delay.
  2. Running some code after an animation has finished.
  3. Running some code when a download has finished.
  4. Running some code when a user has selected an option from your menu.

Closures let us wrap up some functionality in a single variable, then store that somewhere. We can also return it from a function, and store the closure somewhere else.

When you’re learning, closures are a little hard to read – particularly when they accept and/or return their own parameters. But that’s OK: take small steps, and backtrack if you get stuck, and you’ll be fine.

Hacking with Swift is sponsored by NSSpain

SPONSORED Announcing NSSpain 2020: Remote Edition! An online, continuous conference for iOS developers. We’ll start on Thursday and finish on Friday, with talks, activities, and lots of fun for 36 hours, non-stop. Sound good? Join us!

Find out more

Sponsor Hacking with Swift and reach the world's largest Swift community!

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!

Link copied to your pasteboard.