🔶 Swift LanguageBeginnerSwift 1.0+

Optionals

Represent a value that may be missing, and unwrap it safely with if let, guard let and ??.

An optional is a type that holds either a value or nil. You write it by adding ? to a type: String? means "a String, or nothing".

Swift forces you to unwrap optionals before use. Prefer if let or guard let for safe unwrapping, ?? to provide a default, and optional chaining (?.) to call through values that might be nil.

Since Swift 5.7 you can use the shorthand if let name { } instead of if let name = name { }.

optionals.swift

1struct User {
2    let name: String
3    let nickname: String?
4}
5
6func greeting(for user: User?) -> String {
7    guard let user else { return "Hello, guest" }
8
9    if let nickname = user.nickname {
10        return "Hey \(nickname)!"
11    }
12    return "Hello, \(user.name)"
13}
14
15let count = Int("42") ?? 0          // default value
16let maybeUser: User? = User(name: "Sam", nickname: nil)
17let upper = maybeUser?.nickname?.uppercased() // optional chaining → nil

Common pitfalls

Avoid force unwrapping (!) outside of tests and truly impossible cases — it crashes at runtime when nil.
Implicitly unwrapped optionals (String!) are mostly legacy; prefer regular optionals.

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Common pitfalls

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