UPGRADE YOUR SKILLS: Learn advanced Swift and SwiftUI on Hacking with Swift+! >>

Use the guard keyword for early returns

Available from Swift 2.0

Paul Hudson      @twostraws

It's very common to place some conditional checks at the start of a method to ensure that various data is configured ready to go. For example, if a Submit button is tapped, you might want to check that the user has entered a username in your user interface. To do this, you'd use this code:

func submitTapped() {
    guard username.text.characters.count > 0 else {
        return
    }

    print("All good")
}

Using guard might not seem much different to using if, but with guard your intention is clearer: execution should not continue if your conditions are not met. Plus it has the advantage of being shorter and more readable, so guard is a real improvement, and I'm sure it will be adopted quickly.

There is one bonus to using guard that might make it even more useful to you: if you use it to unwrap any optionals, those unwrapped values stay around for you to use in the rest of your code block. For example:

guard let unwrappedName = userName else {
    return
}

print("Your username is \(unwrappedName)")

This is in comparison to a straight if statement, where the unwrapped value would be available only inside the if block, like this:

if let unwrappedName = userName {
    print("Your username is \(unwrappedName)")
} else {
    return
}

// this won't work – unwrappedName doesn't exist here!
print("Your username is \(unwrappedName)")

BUILD THE ULTIMATE PORTFOLIO APP Most Swift tutorials help you solve one specific problem, but in my Ultimate Portfolio App series I show you how to get all the best practices into a single app: architecture, testing, performance, accessibility, localization, project organization, and so much more, all while building a SwiftUI app that works on iOS, macOS and watchOS.

Get it on Hacking with Swift+

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

Other changes in Swift 2.0…

Download all Swift 2.0 changes as a playground Link to Swift 2.0 changes

Browse changes in all Swift versions

 
Unknown user

You are not logged in

Log in or create account
 

Link copied to your pasteboard.