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

Unwrapping optionals

Optional strings might contain a string like “Hello” or they might be nil – nothing at all.

Consider this optional string:

var name: String? = nil

What happens if we use name.count? A real string has a count property that stores how many letters it has, but this is nil – it’s empty memory, not a string, so it doesn’t have a count.

Because of this, trying to read name.count is unsafe and Swift won’t allow it. Instead, we must look inside the optional and see what’s there – a process known as unwrapping.

A common way of unwrapping optionals is with if let syntax, which unwraps with a condition. If there was a value inside the optional then you can use it, but if there wasn’t the condition fails.

For example:

if let unwrapped = name {
    print("\(unwrapped.count) letters")
} else {
    print("Missing name.")
}

If name holds a string, it will be put inside unwrapped as a regular String and we can read its count property inside the condition. Alternatively, if name is empty, the else code will be run.

Subscribe to Hacking with Swift+

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: 4.5/5

Link copied to your pasteboard.