You can get the code for our photo book app by visiting: https://github.com/SwiftProgrammingCookbook/PhotobookCreator, and choosing the start-operations branch, or you can use git:
git clone https://github.com/SwiftProgrammingCookbook/PhotobookCreator.git
git checkout start-operations
Open the project in Xcode, and navigate to the PhotoCollectionViewController.swift file.