Swift 5.1: Function Cheat Sheet

// A Void function
func sayHello() {
  print("Hello")
}
// Function with parameters
func sayHello(name: String) {
  print("Hello (name)!")
}
// Function with default parameters
func sayHello(name: String = "Lorenzo") {
  print("Hello (name)!")
}
// Function with mix of default and
// regular parameters
func sayHello(name: String = "Lorenzo", age: Int) {
  print("(name) is (age) years old!")
}
// Using just the non default value
sayHello(age: 35)
// Function with parameters and return value
fune add(x: Int, y: Int) -> Int {
  return x + y
}
let value = add(x: 8, y: 10)
// If the function contains a single expression,
// the return value can be omitted
func multiply(x: Int, y: Int) —> Int {
  x * y
}
// Specifying arguments labels
func add(x xVal: Int, y yVal: Int) -> Int {
  return xVal + yVal
}
// Omitting the argument label for one
// (or more) parameters
fune add(_ x: Int, y: Int) -> Int {
  return x + y
}
let value = add(8, y: 10)
// A function that accepts another function
func doMath(operation: (Int, Int) -> Int, a: Int, b: Int) —> Int {
  return operation(a, b)
}