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Hands-On Design Patterns with Swift
Hands-On Design Patterns with Swift

Hands-On Design Patterns with Swift: Master Swift best practices to build modular applications for mobile, desktop, and server platforms

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Profile Icon Vilmart Profile Icon De Simone Profile Icon Giordano Scalzo
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€36.99
Paperback Dec 2018 414 pages 1st Edition
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Arrow left icon
Profile Icon Vilmart Profile Icon De Simone Profile Icon Giordano Scalzo
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€36.99
Paperback Dec 2018 414 pages 1st Edition
eBook
€20.98 €29.99
Paperback
€36.99
Subscription
Free Trial
Renews at €18.99p/m
eBook
€20.98 €29.99
Paperback
€36.99
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Free Trial
Renews at €18.99p/m

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Hands-On Design Patterns with Swift

Understanding ARC and Memory Management

Swift has a very particular and almost unique memory management strategy: Automatic Reference Counting (ARC). When using ARC, the compiler will inject memory management code for us, but it's very easy to write poor, leaky code, either on purpose or by accident. In this chapter, we'll cover all of the basics for good memory management in Swift. From its origins in Objective-C, to the pre-ARC era, to today, we'll look at how to properly manage our memory and object life cycles. We'll also explore the powerful tools available with Xcode to track memory usage, leaks, cycles, and other defects, through the inspector and the leaks instrument.

In this chapter, we'll cover the following topics:

  • A brief history of reference counting
  • What is ARC?
  • Debugging memory
  • Leaks, cycles, and dangling references
...

A brief history of reference counting

Before we get into the details of ARC, we need to rewind the time machine to a previous epoch. The year is 1988, and Objective-C is licensed by NeXT and starting to make its way into their operating system. In 1996, Apple acquires NeXT, alongside the release of OS X, a new and modern toolchain based on Objective-C. Objective-C is a strict superset of C, which means that any valid C code is valid Objective-C code, but unlike C, Objective-C has a modern and efficient memory management engine, based on reference counting.

Reference counting is a technique that accounts for the exact number of references to a particular object that exist at any given time in the memory. Once there are no references, an object, it is deallocated. This is a very different memory management technique, as compared to garbage collection, which you can find in Java...

ARC – what is that?

Automatic Reference Counting was introduced at the 2011 WWDC, in Session 323. If you want to see the original presentation, feel free to visit https://developer.apple.com/videos/play/wwdc2011/323/

ARC is made possible by Clang and LLVM. LLVM and Clang are two technologies that enable compiling C, C++, and Objective-C code. LLVM is also used alongside the Swift compiler. With ARC, a Clang feature, developers don't have to write the tedious retain and release calls. There are multiple benefits to letting the compiler handle it, as follows:

  • Memory management is difficult
  • The compiler is often more correct than you are
  • There are fewer lines of code to write
  • It has the same performance as manual reference counting

With Swift being a modern language and the successor of Objective-C, you've never had to call retain. Swift programs...

Memory debugging

Xcode and Swift come with a powerful memory debugging infrastructure, letting you inspect the contents of existing and destroyed objects, inspect the contents and relationships between your objects, and more. In this section, we'll get you started with these powerful tools, so that later on, you'll be able to debug complicated pieces of code with ease.

Configuring your project

In order to see the memory allocation backtraces, we need to enable Malloc Stack in our Scheme. You can do so by following these steps:

  1. Open your Scheme settings with ⌘ | <, or by navigating to Product | Scheme | Edit Scheme...
  2. Navigate to the Diagnostics tab
  1. Ensure that you select the options shown in the...

Leaks, cycles, and dangling references

Let's dive into examples of the two most common issues: leaks and crashes related to memory issues. A memory leak occurs when one or many objects become unreachable from the rest of your program but still, in one way or another, form a cycle.

In the first example, we'll look at how to effectively leak memory, using Xcode's powerful memory graph hierarchy tool to track down issues.

In the second example, we'll explore how to debug and investigate crashes related to accessing properties that may have been deallocated.

Leaking with cycles

One common way to leak objects and their memory is to create strong references between different instances, and cut off any external...

Summary

In this chapter, we explored the origins of ARC, the performant memory management paradigm available in Swift. With great power comes great responsibility, so you're still required to design your memory model with ARC in mind; failing to do so will lead to memory leaks or crashes caused by dangling pointers. By now, you should be comfortable with the advantages and drawbacks of both weak and unowned references. You should also understand why weak or unowned don't apply to value types. Last but not least, you should now be comfortable with setting your project up to efficiently debug memory with the tools from Xcode.

ARC sits at the compiler level, injected into your code as it is built. In the next chapter, we'll continue to refresh the basics and stretch our muscles, as we explore Foundation and the standard library.

...
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Key benefits

  • Write clean, reusable and maintainable code, and make the most of the latest Swift version.
  • Analyze case studies of some of the popular open source projects and give your workflow a huge boost
  • Choose patterns such as MVP, MVC, and MVVM depending on the application being built

Description

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.

Who is this book for?

This book is for intermediate developers who want to apply design patterns with Swift to structure and scale their applications. You are expected to have basic knowledge of iOS and Swift.

What you will learn

  • Work efficiently with Foundation and Swift Standard library
  • Understand the most critical GoF patterns and use them efficiently
  • Use Swift 4.2 and its unique capabilities (and limitations) to implement and improve GoF patterns
  • Improve your application architecture and optimize for maintainability and performance
  • Write efficient and clean concurrent programs using futures and promises, or reactive programming techniques
  • Use Swift Package Manager to refactor your program into reusable components
  • Leverage testing and other techniques for writing robust code
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Publication date : Dec 24, 2018
Length: 414 pages
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Language : English
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Length: 414 pages
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Table of Contents

16 Chapters
Refreshing the Basics Chevron down icon Chevron up icon
Understanding ARC and Memory Management Chevron down icon Chevron up icon
Diving into Foundation and the Standard Library Chevron down icon Chevron up icon
Working with Objective-C in a Mixed Code Base Chevron down icon Chevron up icon
Creational Patterns Chevron down icon Chevron up icon
Structural Patterns Chevron down icon Chevron up icon
Behavioral Patterns Chevron down icon Chevron up icon
Swift-Oriented Patterns Chevron down icon Chevron up icon
Using the Model-View-Controller Pattern Chevron down icon Chevron up icon
Model-View-ViewModel in Swift Chevron down icon Chevron up icon
Implementing Dependency Injection Chevron down icon Chevron up icon
Futures, Promises, and Reactive Programming Chevron down icon Chevron up icon
Modularize Your Apps with Swift Package Manager Chevron down icon Chevron up icon
Testing Your Code with Unit and UI Tests Chevron down icon Chevron up icon
Going Out in the Open (Source) Chevron down icon Chevron up icon
Other Books You May Enjoy Chevron down icon Chevron up icon
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