How to write a closure that returns a value

Swift version: 5.1

Paul Hudson    @twostraws    May 28th 2019

Like regular functions, closures can accept values and return values of your choosing: just write them out at the start of your closure, followed by the word in.

For example, we could write a greeting closure that accepts the name of a person to greet and returns a string using that name:

let greeting = { (name: String) -> String in
    return "Hello, \(name)!"
}

You can now call that just like any other function, passing in someone’s name as its only parameter:

let message = greeting("Taylor")

Available from iOS 8.0

Similar solutions…

• What is a monad?
• What is the @GestureState property wrapper?
• Two-way bindings in SwiftUI
• How to modify haptic events over time using CHHapticParameterCurve
• What is trailing closure syntax?

About the Swift Knowledge Base

This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.