Swift Programming: The Big Nerd Ranch Guide

18 Value vs Reference Types

This chapter builds on the lessons you have been learning about value types, like structs, and references types, like classes. You will explore the differences between the two by comparing their differing behaviors in a variety of scenarios. At the end of this chapter, you should have a good understanding of when to use a value type or a reference type.

Value Semantics

Create a new playground called ValueVsRefs. Your playground has the usual template code:

import Cocoa

var str = "Hello, playground"

You have seen this code many times before: You have a mutable instance of type String set to the value of "Hello, playground". Make a new string by giving the value of str to another instance. ...