Swift Programming: The Big Nerd Ranch Guide, 3rd Edition

Strong Reference Cycles

To start, you will define the types you will be interacting with: Vault and Asset. You will create one vault and multiple assets to put into the vault, and then you will observe how your code affects their lifetimes.

You are going to create a new file to model your vault. First, in the project navigator on the left side of the Xcode screen, click the yellow CyclicalAssets folder. This will ensure that the file appears in the correct location in your project. Next, create a new Swift file, Vault.swift, and define a Vault class that conforms to the CustomStringConvertible protocol:

Example 24.1. Defining the Vault class (Vault.swift)

import Foundation

class Vault { let number: Int init(number: Int) { self.number = number ...