Declare A Function

A function is a reusable block of code that performs a specific task. Instead of writing the same code multiple times, you define it once in a function and call it whenever needed.

In Swift, you declare a function using the func keyword, followed by the function name and parentheses:

func sayHello() {
    print("Hello!")
}

sayHello()  // Output: Hello!
sayHello()  // Output: Hello!

The code inside the curly braces { } is the function body—it runs each time you call the function. To call a function, simply write its name followed by parentheses.

Functions help organize your code and make it more readable. If you need to change how something works, you only update it in one place rather than everywhere it's used.

func greetUser() {
    print("Welcome!")
    print("Glad to have you here.")
}

greetUser()

A function can contain any code you've learned so far—variables, loops, conditionals—all bundled together under a meaningful name.