NEW: My new book Pro SwiftUI is out now – level up your SwiftUI skills today! >>

Multiple trailing closures

Available from Swift 5.3

Paul Hudson      @twostraws

SE-0279 introduced multiple trailing closures, making for a simpler way to call a function with several closures.

This will be particularly welcome in SwiftUI, where code like this:

struct OldContentView: View {
    @State private var showOptions = false

    var body: some View {
        Button(action: {
            self.showOptions.toggle()
        }) {
            Image(systemName: "gear")
        }
    }
}

Can now be written as this:

struct NewContentView: View {
    @State private var showOptions = false

    var body: some View {
        Button {
            self.showOptions.toggle()
        } label: {
            Image(systemName: "gear")
        }
    }
}

Technically there is no reason why label: needs to be on the same line as the preceding }, so you could even write this if you wanted:

struct BadContentView: View {
    @State private var showOptions = false

    var body: some View {
        Button {
            self.showOptions.toggle()
        }

        label: {
            Image(systemName: "gear")
        }
    }
}

However, I would caution against that for readability – a floating piece of code like that is never pleasant, and in Swift it looks like a labeled block rather than a second parameter to the Button initializer.

Hacking with Swift is sponsored by Stream

SPONSORED Build Chat messaging quickly with Stream Chat. The Stream iOS Chat SDK is highly flexible, customizable, and crazy optimized for performance. Take advantage of this top-notch developer experience, get started for free today!

Click here

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

Other changes in Swift 5.3…

Download all Swift 5.3 changes as a playground Link to Swift 5.3 changes

Browse changes in all Swift versions

 
Unknown user

You are not logged in

Log in or create account
 

Link copied to your pasteboard.