Swift functions

up:: Swift ⚐

Named parameters and labels

Swift requires specifying parameter names

JavaScript Functions generally¹ don’t use named parameters:

function sayHello(name: string, day: string) {
	return `Hello ${name}, the day is ${day}`
}
 
// called with
sayHello("John", "Tuesday")

But in Swift, we have to specify the parameter name:

func sayHello(name: String, day: String) -> String {
    return "Hello \(name), the day is \(day)"
}
 
// called with
sayHello(name: "John", day: "Tuesday")

Using labels for parameter names

By prepending a string before the parameter name, we add a label.

func sayHello(to name: String, onDay day: String) -> String {
    return "Hello \(name), the day is \(day)"
}
 
// called with
sayHello(to: "John", onDay: "Tuesday")

Ideally, function names and parameter labels combine to make function calls similar to sentences.

Argument labels can be blank

func say(_ message: String) {
	print("I say: '\(message)'")
}
say("Hello")

This way Swift functions behave more like JavaScript functions.

Links

• Why does Swift use parameter labels? - a free Understanding Swift tutorial
• Learn swift in Y Minutes

Footnotes

1. Although you can simulate it with parameter destructuring, or other hackery. ↩