Swift Academy · Lesson

The Nil-Coalescing Operator

Supply a default when an optional is nil.

Lesson 1 of 413 steps

The Nil-Coalescing Operator is a free Swift Academy lesson on CoddyKit. This is lesson 1 of 4. Any 3 lessons of this learning path are free to read in full — after that, CoddyKit PRO unlocks every lesson, plus hands-on practice with a built-in code editor and a 24/7 AI tutor. It is part of the Swift Academy learning path, and your progress syncs across the web and the CoddyKit app. The Swift Academy course includes 4 lessons in total.

The Problem of nil

An optional may hold a value or be nil. Often you want to use the value if present, or fall back to a default if it is nil.

let typedName: String? = nil
let name = typedName ?? "Guest"
print(name)

The ?? Operator

The nil coalescing operator ?? takes an optional on the left and a default on the right. If the optional is non-nil, you get its unwrapped value; otherwise you get the default.

let stored: Int? = 42
let value = stored ?? 0
print(value)

Default Is Used Only on nil

The right-hand default is only used when the left side is nil. A present value, even 0 or an empty string, is kept.

let count: Int? = 0
let result = count ?? 99
print(result)

Result Is Non-Optional

The expression optional ?? default produces a non-optional value, because there is always something to fall back to.

let nickname: String? = nil
let display: String = nickname ?? "Anonymous"
print(display)

Replacing if let

Without ?? you would write an if/else to unwrap and provide a default. Nil coalescing collapses that into one expression.

let age: Int? = nil
var finalAge: Int
if let unwrapped = age {
    finalAge = unwrapped
} else {
    finalAge = 18
}
print(finalAge)

Same Logic With ??

Here is the previous example rewritten with nil coalescing. It is shorter and the intent is obvious.

let age: Int? = nil
let finalAge = age ?? 18
print(finalAge)

Coalescing in Interpolation

You can drop ?? directly inside string interpolation to print a friendly fallback.

let city: String? = nil
print("City: \(city ?? "Unknown")")

From Failable Conversions

Converting a String to an Int returns an optional. Nil coalescing gives a default when the text is not a number.

let text = "abc"
let number = Int(text) ?? -1
print(number)

Coalescing With Dictionaries

Looking up a key in a dictionary returns an optional. Use ?? to supply a fallback when the key is missing.

let scores = ["Ann": 90]
let bob = scores["Bob"] ?? 0
print(bob)

The Default Can Be Computed

The right side can be any expression of the right type, even a function call. It is only evaluated when needed.

func defaultName() -> String {
    return "Player1"
}
let entered: String? = nil
print(entered ?? defaultName())

Type Must Match

The default must be compatible with the optional wrapped type. An Int? needs an Int default.

let maybe: Int? = nil
let safe = maybe ?? 100
print(safe + 1)

Quick Check

Test nil coalescing.

Answer it in the interactive lesson

Recap: The Nil Coalescing Operator

The ?? operator unwraps an optional or falls back to a default, producing a non-optional result. The default is only used when the optional is nil.

let input: String? = nil
let name = input ?? "Default"
print(name)

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Frequently Asked Questions

Is the “The Nil-Coalescing Operator” lesson free?

Yes — any 3 lessons of the Swift Academy learning path, including “The Nil-Coalescing Operator”, are free to read in full here on the web. After that, CoddyKit PRO unlocks every lesson, plus interactive practice with a built-in code editor and a 24/7 AI tutor. The Swift Academy course includes 4 lessons in total.

What will I learn in “The Nil-Coalescing Operator”?

Supply a default when an optional is nil. You practise Swift Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Swift Academy?

No prior experience is required. Swift Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 1 of 4.

How long does the “The Nil-Coalescing Operator” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Swift Academy lesson?

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