Swift Programming: The Big Nerd Ranch Guide

Function Types

Each function you have been working with in this chapter has a specific type. In fact, all functions do. Function types are made up of the function’s parameter and return types. Consider the sortedEvenOddNumbers(_:) function. This function takes an array of integers as an argument and returns a tuple with two arrays of integers. Thus, the function type for sortedEvenOddNumbers(_:) is expressed as ([Int]) -> ([Int], [Int]).

The function’s parameters are listed inside the left parentheses, and the return type comes after the ->. You can read this function type as: “A function with one parameter that takes an array of integers and returns a tuple with two arrays containing integers.” For comparison, a function with no arguments ...