Functions in Swift
From the Swift cheat sheet · Functions & Closures · verified Jul 2026
Functions
Function declaration and parameters
swift
// Basic function
func greet(name: String) -> String {
return "Hello, \(name)!"
}
// Multiple parameters and labels
func greet(person: String, from hometown: String) -> String {
return "Hello \(person) from \(hometown)"
}
greet(person: "Alice", from: "NYC")
// Default parameters
func increment(number: Int, by amount: Int = 1) -> Int {
return number + amount
}
// Variadic parameters
func sum(numbers: Int...) -> Int {
return numbers.reduce(0, +)
}💡 Use argument labels for clarity at call sites
⚡ Inout parameters allow functions to modify values
📌 Functions are first-class types in Swift
🟢 @discardableResult suppresses unused return value warnings