When to use inout parameters?

Question

When passing a class or primitive type into a function, any change made in the function to the parameter will be reflected outside of the class. This is basically the same t

Answer 1

inout means that modifying the local variable will also modify the passed-in parameters. Without it, the passed-in parameters will remain the same value. Trying to think of reference type when you are using inout and value type without using it.

For example:

import UIKit

var num1: Int = 1
var char1: Character = "a"

func changeNumber(var num: Int) {
    num = 2
    print(num) // 2
    print(num1) // 1
}
changeNumber(num1)

func changeChar(inout char: Character) {
    char = "b"
    print(char) // b
    print(char1) // b
}
changeChar(&char1)

A good use case will be swap function that it will modify the passed-in parameters.

Swift 3+ Note: Starting in Swift 3, the inout keyword must come after the colon and before the type. For example, Swift 3+ now requires func changeChar(char: inout Character).