NEW! Pre-order my latest book, Testing Swift! >>

What is the nil coalescing operator?

Paul Hudson       @twostraws

Optionals are a powerful source of safety in Swift, but can also be annoying if you find them littered throughout your code. Swift's nil coalescing operator helps you solve this problem by either unwrapping an optional if it has a value, or providing a default if the optional is empty.

Here's an example to get you started:

let name: String? = nil
let unwrappedName = name ?? "Anonymous"

Because name is an optional string, we need to unwrap it safely to ensure it has a meaningful value. The nil coalescing operator – ?? – does exactly that, but if it finds the optional has no value then it uses a default instead. In this case, the default is "Anonymous". What this means is that unwrappedName has the data type String rather than String? because it can be guaranteed to have a value.

You don't need to create a separate variable to use nil coalescing. For example, this works fine too:

print("Hello, \(name ?? "Anonymous")!")

Available from iOS 7.0

Did this solution work for you? Please pass it on!

Other people are reading…

About the Swift Knowledge Base

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

Need to know Objective-C fast?

I wrote a book dedicated to teaching Objective-C to developers who already know Swift – it's the fastest way to get up to speed!

MASTER SWIFT NOW
Buy Testing Swift Buy Practical iOS 12 Buy Pro Swift Buy Swift Design Patterns Buy Swift Coding Challenges Buy Server-Side Swift (Vapor Edition) Buy Server-Side Swift (Kitura Edition) Buy Hacking with macOS Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with Swift Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Beyond Code

Was this page useful? Let me know!

Average rating: 3.5/5

Click here to visit the Hacking with Swift store >>