# ??(_:_:) Performs a nil-coalescing operation, returning the wrapped value of an `Optional` instance or a default `Optional` value. ``` func ?? (optional: consuming T?, defaultValue: @autoclosure () throws -> T?) rethrows -> T? where T : ~Copyable ``` ## Parameters `optional` An optional value. `defaultValue` A value to use as a default. `defaultValue` and `optional` have the same type. ## Discussion A nil-coalescing operation unwraps the left-hand side if it has a value, or returns the right-hand side as a default. The result of this operation will be the same type as its arguments. This operator uses short-circuit evaluation: `optional` is checked first, and `defaultValue` is evaluated only if `optional` is `nil`. For example: ``` let goodNumber = Int("100") ?? Int("42") print(goodNumber) // Prints "Optional(100)" let notSoGoodNumber = Int("invalid-input") ?? Int("42") print(notSoGoodNumber) // Prints "Optional(42)" ``` In this example, `goodNumber` is assigned a value of `100` because `Int("100")` succeeds in returning a non-`nil` result. When `notSoGoodNumber` is initialized, `Int("invalid-input")` fails and returns `nil`, and so `Int("42")` is called to supply a default value. Because the result of this nil-coalescing operation is itself an optional value, you can chain default values by using `??` multiple times. The first optional value that isn’t `nil` stops the chain and becomes the result of the whole expression. The next example tries to find the correct text for a greeting in two separate dictionaries before falling back to a static default. ``` let greeting = userPrefs[greetingKey] ?? defaults[greetingKey] ?? "Greetings!" ``` If `userPrefs[greetingKey]` has a value, that value is assigned to `greeting`. If not, any value in `defaults[greetingKey]` will succeed, and if not that, `greeting` will be set to the non-optional default value, `"Greetings!"`. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)