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

Accepting parameters in a closure

When you create closures, they don’t have a name or space to write any parameters. That doesn’t mean they can’t accept parameters, just that they do so in a different way: they are listed inside the open braces.

To make a closure accept parameters, list them inside parentheses just after the opening brace, then write in so that Swift knows the main body of the closure is starting.

For example, we could make a closure that accepts a place name string as its only parameter like this:

let driving = { (place: String) in
    print("I'm going to \(place) in my car")
}

One of the differences between functions and closures is that you don’t use parameter labels when running closures. So, to call driving() now we’d write this:

driving("London")
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!

Average rating: 4.8/5

Link copied to your pasteboard.