Parameters And Arguments

Functions become much more powerful when they can accept input. Parameters are placeholders defined in the function declaration, while arguments are the actual values you pass when calling the function.

To add a parameter, specify its name and type inside the parentheses:

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

greet(name: "Alice")  // Output: Hello, Alice!
greet(name: "Bob")    // Output: Hello, Bob!

Here, name: String is the parameter—it tells Swift the function expects a String value. When calling the function, you provide the argument using the parameter name followed by a colon.

Functions can accept multiple parameters, separated by commas:

func introduce(name: String, age: Int) {
    print("\(name) is \(age) years old.")
}

introduce(name: "Sara", age: 25)
// Output: Sara is 25 years old.

Each parameter acts like a constant inside the function body—you can use it but not modify it. The order of arguments must match the order of parameters in the function definition.