Book Image

Hands-On Design Patterns with Swift

By : Florent Vilmart, Giordano Scalzo, Sergio De Simone
Book Image

Hands-On Design Patterns with Swift

By: Florent Vilmart, Giordano Scalzo, Sergio De Simone

Overview of this book

Swift keeps gaining traction not only amongst Apple developers but also as a server-side language. This book demonstrates how to apply design patterns and best practices in real-life situations, whether that's for new or already existing projects. You’ll begin with a quick refresher on Swift, the compiler, the standard library, and the foundation, followed by the Cocoa design patterns – the ones at the core of many cocoa libraries – to follow up with the creational, structural, and behavioral patterns as defined by the GoF. You'll get acquainted with application architecture, as well as the most popular architectural design patterns, such as MVC and MVVM, and learn to use them in the context of Swift. In addition, you’ll walk through dependency injection and functional reactive programming. Special emphasis will be given to techniques to handle concurrency, including callbacks, futures and promises, and reactive programming. These techniques will help you adopt a test-driven approach to your workflow in order to use Swift Package Manager and integrate the framework into the original code base, along with Unit and UI testing. By the end of the book, you'll be able to build applications that are scalable, faster, and easier to maintain.
Table of Contents (22 chapters)
Title Page
Copyright and Credits
About Packt
Contributors
Preface
Index

Basics of the MVVM pattern


The MVVM pattern involves three different components. You should be familiar with two of them:

  • Model: This is the same model as in MVC, and it represents knowledge and data.
  • View: This is the same as in the MVC pattern; it provides an external representation that is understandable by the user, whether human or machine.
  • ViewModel: This is the model for a view (duh!). It represents the whole state of the view, and exposes behaviors.

Note

What about UIViewControllers and NSViewControllers? They belong to the View layer (think back to the previous chapter). We will inject ViewModels in either the views or the viewControllers.

Refactoring MVC into MVVM

We will reuse the previous example, the Question/Answer game, but this time, instead of writing it following a pure MVC pattern, we'll use the MVVM pattern.

As with the previous implementation (with the MVC pattern), we'll cover each layer, one after the other, in order to not miss anything.

Model

The model layer still contains...