Writing a Function

In this lesson you will learn the basic way to define a function in Swift so you can reuse the same logic over and over. This is for anyone searching for "Swift functions how to use".

You define a function with func name(label: Type) -> ReturnType. Argument labels are what make a Swift function call read almost like natural English.

The sample code has greet take a name: String argument and return a greeting, with the return type stated explicitly as -> String. Writing the return type with -> makes the intent of the code much clearer.

A common stumbling block for beginners is the difference between the argument label and the internal parameter name. At the call site you write the label, as in greet(name: "Bob"), but the label does not have to match the name used inside the function.

In real-world development, gathering shared logic into functions reduces duplication and means a fix only has to be made in one place.

📖 Reference code

func greet(name: String) -> String {
    return "Welcome, \(name)!"
}
print(greet(name: "Bob"))

✍️ Your code

Type your code, then press "Run"

🧪 This site can't compile or run Swift directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).