Accepting parameters

Functions become more powerful when they can be customized each time you run them. Swift lets you send values to a function that can then be used inside the function to change the way it behaves. We’ve used this already – we’ve been sending strings and integers to the print() function, like this:

print("Hello, world!")

Values sent into functions this way are called parameters.

To make your own functions accept parameters, give each parameter a name, then a colon, then tell Swift the type of data it must be. All this goes inside the parentheses after your function name.

For example, we can write a function to print the square of any number:

func square(number: Int) {
    print(number * number)
}

That tells Swift we expect to receive an Int, and it should be called number. This name is used both inside the function when you want to refer to the parameter, but also when you run the function, like this: