Swift (Programming Language)

Swift is a compiled, statically typed programming language introduced by Apple in 2014 as the successor to Objective-C for its platforms. It is open source and also runs on Linux and Windows, though it is used mostly for iOS, iPadOS, macOS, watchOS and tvOS apps.

Why it matters

Swift is the main language for native Apple apps, typically paired with the SwiftUI or UIKit frameworks. It was designed for safety: variables must be initialized before use, integer overflow traps instead of silently wrapping, and optionals make the possible absence of a value explicit in the type. It manages memory with automatic reference counting rather than a tracing garbage collector.

Example

let input: String? = "42"

if let text = input, let n = Int(text) {
    print(n + 1)   // 43
} else {
    print("not a number")
}

String? is an optional that may hold nil. if let unwraps it safely only when a value exists.

Common mistakes

• Force-unwrapping optionals with !, which crashes the app when the value is nil.
• Creating retain cycles between closures and objects, leaking memory.
• Doing UI updates off the main thread.

Related

• iOS
• Null
• Memory leak
• Closure

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