Module 6: Functions in Swift – Defining, Calling & Returning Values

Module 6: Functions in Swift

Functions are reusable blocks of code that perform specific tasks. In Swift, functions help you organize your code into manageable, logical parts. They can accept input parameters and return values, making your code modular and efficient.

Defining and Calling Functions

You define a function using the func keyword, followed by the function name and parentheses. Inside the parentheses, you specify parameters if needed.

func greet() {
    print("Hello, Swift learner!")
}

greet()  // Calling the function

Functions with Parameters

Functions can accept input parameters to perform tasks with different values.

func greet(name: String) {
    print("Hello, \(name)!")
}

greet(name: "Alice")

Functions with Return Values

Functions can return values using the -> syntax.

func add(a: Int, b: Int) -> Int {
    return a + b
}

let sum = add(a: 5, b: 3)
print(sum)  // Output: 8

Parameter Labels and Omitting Labels

Swift allows external parameter labels for clarity when calling functions.

func greet(person name: String) {
    print("Hello, \(name)!")
}

greet(person: "Bob")

To omit labels, use an underscore _:

func greet(_ name: String) {
    print("Hello, \(name)!")
}

greet("Charlie")

Functions with Multiple Return Values

Use tuples to return multiple values from a function.

func getMinMax(numbers: [Int]) -> (min: Int, max: Int)? {
    guard let first = numbers.first else { return nil }
    var min = first
    var max = first
    for number in numbers {
        if number < min { min = number } else if number > max {
            max = number
        }
    }
    return (min, max)
}

if let result = getMinMax(numbers: [3, 7, 2, 9, 5]) {
    print("Min: \(result.min), Max: \(result.max)")
}

Nested Functions

Functions can be defined inside other functions for encapsulation.

func outer() {
    func inner() {
        print("Inner function called")
    }
    inner()
}

outer()

Functions as First-Class Citizens

Functions can be assigned to variables and passed as arguments.

func square(number: Int) -> Int {
    return number * number
}

let myFunc = square
print(myFunc(4))  // Output: 16

Summary

• Functions help organize reusable code blocks.
• Functions can take parameters and return values.
• Parameter labels improve readability.
• Functions can return multiple values using tuples.
• Nested functions and function variables increase flexibility.