Mastering React Native

Table of Contents

Mastering React Native

Credits

Disclaimer

About the Authors

About the Reviewer

www.PacktPub.com

Why subscribe?

Customer Feedback

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Downloading the example code

Errata

Piracy

Questions

1. Building a Foundation in React

Library versus framework

Motivation for React

Getting started in React

Describing components in JSX

The component

Component composition

Props and PropTypes

Accepting props

PropTypes

Passing props

Default props

Props.children

Event handlers

State

The component lifecycle

The update cycle

Unmounting the component

Alternate component forms

React.createClass

Functional components

Summary

2. Saying HelloWorld in React Native

Understanding the mobile app development ecosystem

Adobe PhoneGap

Ionic

NativeScript

React Native

Extending React Native

Introducing style and layout in React Native

Understanding all the React Native tools

Xcode

Google Chrome

Homebrew (also known as brew)

Node.js and npm

Watchman

Flow

React Native command-line interface (CLI)

Installing our tools

Installing Xcode

Installing Homebrew

Installing Node and npm

Installing Watchman and Flow

Installing the React Native CLI

Creating our first React Native app

React Native Packager

Understanding our HelloWorld app

Importing dependencies using ECMAScript 2015

Our HelloWorld component

HelloWorld style code

Registering the root component

Why import React?

Debugging a React Native app

Enabling the Chrome Debugger

Breakpoints

Summary

3. Styling and Layout in React Native

Constructing and applying styles

Inline styles

Styles as objects in your React Native components

Stylesheet

Using Stylesheet.hairlineWidth

Applying component-specific style properties

Styling without inheritance

Understanding React Native's take on the box model and flexbox

Box model

Understanding Flexbox

Covering the other axis

Flex shrinking and growing

Setting flexBasis

Growing and shrinking flex items

Styling text with React Native

Text style properties

Encapsulating text styles in reusable components

Styling images

Background images

Inspecting and debugging styles

Using the React Native Inspector

Adding media query behavior to React Native

Using Dimensions

Using onLayout per View

Summary

4. Starting our Project with React Native Components

Native components

Text

Props

View

Props

Image

Props

Static methods

Touchable

Props

ListView

DataSource

renderRow

Props

Modal

Props

WebView

Props

TabBarIOS

Props

TabBarIOS.Item

Props

TextInput

Props

Other input components

Native APIs

ActionSheetIOS

Alert

Vibration

StatusBar

Summary

5. Flux and Redux

The Flux architecture

Motivation

Implementing Flux

Creating our view

Actions and action creators

Dispatcher

Stores

Rendering updated data

Getting started with Redux

Principles of Redux

Installing Redux

Implementing Redux

Refactoring the store

Reducer

Creating the store

Multiple reducers

Action creators

Subscribing to the store

React-Redux

Installing React-Redux

React context and providers

Container and presentational components

Middleware

Summary

6. Integrating with the NYT API and Redux

Understanding the NYT API data

Wiring up our Redux data flow

Creating the Redux state tree

Wiring up Redux data to our app

Refactoring and reshaping

Refactoring the components

Reshaping the data

Introducing Reselect

Adding search

Wiring up the NYT API with asynchronous requests

Fixing iOS transport security

Adding pull to refresh and a loading spinner

Summary

7. Navigation and Advanced APIs

Navigation landscape

NavigatorIOS

Navigator

NavigationExperimental

Choosing a navigator

Using Navigator

The Navigator component

Navigation bar

Advanced navigation with NavigationExperimental

Representing the navigation state

Managing the navigation state

The CardStack component

Navigation header

Tabbed navigation

Adding in the modal

Other advanced APIs

Offline messages with NetInfo

Opening the browser with linking

Saving bookmarks locally with AsyncStorage

Summary

8. Animation and Gestures in React Native

Introducing LayoutAnimation and Animated

Building the basic Onboarding experience

Getting started

Adding LayoutAnimation

Adding a bit more animation

Understanding Animated

Refactoring our Onboarding experience

Adding Animated to our Onboarding experience

Interpolating Animated Values

Using PanResponder with the Animated API

Touching up PanResponder

Summary

9. Refactoring for Android

Installing the necessary tools

Installing the Java Development Kit

Installing Android Studio

Configuring Android Studio

Configuring ANDROID_HOME and your PATH

Verifying that the CPU/ABIs are installed

Starting the Android emulator

Adding Android support to RNNYT

Branching platform logic

Refactoring RNNYT for Android

Fixing Android vibration

Using DrawerLayoutAndroid

Customizing Android styling

Enabling LayoutAnimation

Summary

10. Using and Writing Native Modules

Using native modules

Installing native modules

Using the library

Profile page

Adding the profile to the iOS home screen

Adding the profile to the Android home screen

Writing native modules

Native modules in iOS

Setting up the module

Exporting methods

Communicating with callbacks

Communicating with promises

Communicating with events

Exporting constants

Native modules in Android

Setting up the module

Exporting methods

Communicating with callbacks

Communicating with promises

Communicating with events

Exporting constants

Summary

11. Preparing for Production

Testing

Unit testing

Component testing

Performance

Problematic ListView

Using Perf Monitor

Analyzing a Systrace

The React Perf Library

shouldComponentUpdate and PureRenderMixin

Minimizing the impact of state changes

The ListView data source

Additional optimizations

Unresponsive touch and slow navigation

Mitigating unresponsive touch

Smoothing out animations with InteractionManager

Performance summary

Running on physical devices

Debugging on an iOS device

Testing your app on an iOS device using Release

Debugging on Android devices

Generating a signed APK

Deploying our application

Remove debugging code

iOS

Creating provisioning profiles

Registering an application in iTunes Connect

Adding icons and updating the launch screen

Creating an archive

Beta testing and release

Android

Signing the application

Testing the release build

Generating the APK

Beta-test and release

Summary

12. React Native Tools and Resources

Evaluating React Native Editors, Plugins, and IDEs

Atom and Nuclide

Taking React Native beyond iOS and Android

Introducing React Native Web

Configuring React Native Web

React Native plugin for Universal Windows Platform

Configuring the React Native plugin for UWP

React Native macOS

Configuring React Native macOS

Summary

References

Mastering React Native

Mastering React Native

Copyright © 2017 Packt Publishing

All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author(s), nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.

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Credits

Disclaimer

We are using the New York Times' API for illustrative purposes only. We do not recommend you publish your application to the app store using this API without first reading the Terms of Use (https://developer.nytimes.com/tou). For more information please consult the NYT's terms and conditions.

About the Authors

Eric Masiello is a lead software engineer for Vistaprint Digital. Formerly, Eric worked as a principal frontend engineer for the Advisory Board Company and built mobile apps for the Education Advisory Board. Eric has worked primarily as a frontend/UI developer for over 10 years and freelances as a website designer/developer at http://www.synbydesign.com. He has taught frontend topics at General Assembly in Washington, D.C. and was a technical reviewer for Mastering ReactJS, a video by Packt Publishing.

You can follow him here:

https://www.linkedin.com/in/ericmasiello

https://twitter.com/ericmasiello

http://synbydesign.com

First and foremost, I must extend an enormous thank you to my beautiful, talented, and always-inspiring wife, Hyun. If not for her support, this book would honestly not exist. My deepest gratitude also goes out to my family: Mom, Dad, Brian, Juliana, Nicolas, Umma, and my sisters Hannah, Min, and Carroll. I’m truly blessed to have such a wonderful and supportive family. Shout out to all the inspiring people I’ve had the honor of working with over the years. I’ve learned so much from all of you. Thanks to Keith, Michael, Andrew, Scott, Shelley, Kelly, the inimitable Karthik, Jesse, Jaworski, Beth, Mat, Anbu, Ashwin, Kevin, Ann, all my PIC/RCS homies, the EAB dev/UI team, the entire ABC/EAB UX team, and finally my new Vistaprint Digital family. Thank you to all my close friends who have balanced me, challenged me, shared a drink, or just a laugh: Bryan, Alan, Chris, Kyril, Brandon, April, and the whole Expansion Broadcast + DC crew. Thank you to everyone at Packt for bringing me along on this amazing (and sleepless) journey. And finally, thanks to my coauthor Jacob for all the work he did in realizing this book and for agreeing to even write a book with someone he had known for all of two weeks.

Jacob Friedmann is a developer living in Seattle, WA. He has been working as a developer professionally for 5 years and is currently a principal software engineer at AddThis, an Oracle company. At AddThis, he works on large front and backend applications. He also builds mobile applications using React Native, including Audicy (http://audicy.io), which will soon be launched on the App Store. He has taught several classes, including frontend web development and JavaScript development through General Assembly in Washington D.C.

You can follow him here:

https://www.linkedin.com/in/jacob-friedmann

https://twitter.com/JacobDFriedmann

Writing a book (my first!) is hard, and I don’t think I would have been able to do it without the support of my loving boyfriend, Matt. He weathered my frequent complaining in stride and kept me focused when I needed it most. For that, I am incredibly grateful. Huge thanks to all of my AddThis family who have always inspired me to keep learning and pushed me to do my best work. To all of my friends and family, who were patient with me when I became a recluse to finish this project, thank you. You are loved, and I promise not to do this again for a while! Finally, to Eric for pulling me along on this adventure. I definitely didn’t know what I was getting myself into when I agreed to this, but I can’t imagine having a more dedicated and capable partner.

About the Reviewer

Patrick Puritscher began developing websites at the age of 14 by teaching himself the necessary skills. Already using React.js, he started to develop with React Native, shortly after watching the initial presentation. He is also active in the community with his open source components and recently published an app for iOS, completely written with React Native. After graduating with his bachelor’s degree, Patrick worked as the lead developer for multiple internally used web apps and a website with several million visits each month. It is his personal ambition to create software for people that makes their life easier, rather than making it more difficult with poor UX. Patrick has just started with his master’s degree in Business Informatics. 

You can follow him on:

https://twitter.com/whoispurii

http://patrickpuritscher.com

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Preface

React Native is a library for creating mobile applications using familiar web technologies without sacrificing performance or the look and feel typically associated with fully native applications. It is built on top of Facebook’s open source JavaScript library, React, and indeed, iOS and Android applications created using the library are primarily written in JavaScript. Because one does not need to learn new languages, ecosystems, and best practices for each platform they work on, React Native is pushing the boundaries of what is possible for React developers.

In this book, we will look at the fundamental concepts of React and React Native, as well as the libraries and tools within the React Native ecosystem. We will also work towards the more practical goal of creating a complete React Native application. Finally, we’ll dig into useful and complex React Native concepts such as animation, navigation, native modules, testing and performance analysis. Upon turning over the last page of this book, you’ll be armed with the knowledge to create polished, sophisticated mobile applications using React Native.

What this book covers

Chapter 1, Building a Foundation in React, In order to work effectively in React Native, you must first understand React. This chapter explains the motivation behind React and teaches you how to think in React.

Chapter 2, Saying Hello World in React Native, contains two primary topics. First, we’ll review how React Native works and compare it to other popular mobile development options. Then, we’ll switch gears and focus on configuring your computer to build your first React Native project for iOS.

Chapter 3, Styling and Layout in React Native, React Native borrows many concepts from the web development world, including some of the best parts of Cascading Style Sheets (CSS). It also deliberately avoids some of CSS’s less desirable qualities. This chapter explains how to style React Native apps and how to use Flexbox to layout components.

Chapter 4, Starting our Project with React Native Components, React Native includes many powerful components and APIs. This chapter demonstrates how to use many of these as we begin to build our news reader app, called Readly.

Chapter 5, Flux and Redux, ... The React community has largely eschewed the Model View Controller pattern in favor of a unidirectional data flow pattern called Flux. In this chapter, we’ll help you think in Flux and explain how to leverage a popular Flux implementation known as Redux.

Chapter 6, Integrating with the NYT API and Redux, builds upon what we learned in this chapter. In order to bring our Readly app to life, we’ll implement Redux and Redux middleware as a means of managing our data and communicating with the New York Times API.

Chapter 7, Navigation & Advanced APIs, Navigation in React Native has been a long journey resulting in an abundance of navigation options. But which should you choose? This chapter will make sense of these options. We’ll then apply experimental navigation components along with other advanced React Native APIs to our project.

Chapter 8, Animation and Gestures in React Native, React Native offers two primary ways of creating fluid animations. This chapter will explain how to apply each of these along with touch gesture support to build out an on boarding experience for our Readly app.

Chapter 9, Refactoring for Android, React Native makes cross platform development simple. However, configuring your computer to actually build for Android is a bit less than simple. This chapter will walk you through, step by step, how to install and configure all the tools necessary for Android development. We’ll then revisit our project, refactoring it to both work and feel like a first class Android app.

Chapter 10, Using and Writing Native Modules, One of the most amazing parts of React Native is that it doesn’t limit you to the components and APIs that come packaged with the framework. If you want your app to do something else, you can either bridge custom native code to React Native or include other third-party libraries. This chapter adds additional capabilities to our project by exploring how to create custom native code written in Objective C for iOS and Java for Android.

Chapter 11, Preparing for Production, Discovering the root cause of bug or performance problem can be a real chore. In this chapter we’ll introduce Jest, a testing framework along with other tools for uncovering pesky performance problems. Finally, we’ll show you how to bundle your apps so you can ship them to the iOS and Android stores.

Chapter 12, React Native Tools & Resources, React Native is praised for its awesome developer experience and cross platform support. But can we take React Native even further? In this final chapter, we’ll show off some tools that can improve upon how you build React Native apps. Then we’ll explore a few React Native projects that allow us to extend platform support to the web, macOS, and even Windows.

What you need for this book

While we will add Android support to our project in later chapters, the majority of this book focuses on iOS development. In order to develop for iOS, you must have access to an Apple Mac computer capable of running Xcode 7 or later. Xcode is only necessary for building and testing React Native apps. You’re welcome to edit your code in any editor or IDE of your choosing.

In addition to Xcode, React Native requires a few other tools. These include Homebrew, Node.js (6.5.0 or later), npm (3.10.3 or later), Watchman, the React Native CLI, and Google Chrome for debugging. We’ll explain what all these tools are and how to install them in Chapter 2, Saying Hello World in React Native.

In Chapter 9, Refactoring for Android, we’ll update our project so it can run on both platforms. Android has its own set of software requirements including the Java Development Kit (JDK 1.8 or later) and Android Studio. Once again, we’ll walk you through how to install and configure these tools in Chapter 9, Refactoring for Android.

Finally, in Chapter 12, React Native Tools & Resources, we’ll evaluate software that can aid your React Native workflow and allow you to build React Native apps for even more platforms. All of these installations are completely optional. However, it’s worth noting that the React Native plugin for Universal Windows Platform will require a computer or virtual machine running Windows 10 and Visual Studio 2015 Community.

Who this book is for

It’s expected the reader possess a strong understanding of JavaScript and is familiar with ECMAScript 2015 (ES2015 or ES6). Code samples in this book will heavily leverage ES2015 features such as classes, arrow functions, destructuring, and spreading. Familiarity with React, mobile development, HTML, and CSS will aid in your understanding but are not a requirement.

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Chapter 1. Building a Foundation in React

There is a common trope within the frontend web development community that boils down to new day, new framework. It is a comment on the velocity at which this profession is changing and evolving. The rapid pace can be exhausting, but it is also exciting because of what it represents. The domain of frontend developers seems to be ever expanding-from simple web pages to web applications, mobile applications, and beyond-and with that, the number of smart people contributing ideas and code to the collective knowledge bank is also expanding.     

With all of that said, any sane person must pick and choose which developments to tune into. When React.js emerged on to the open source scene in May 2013 from the inner-sanctum of Facebook, it would have been easy to brush this library off as just another frontend library. That, however, would have been a mistake. It could be said that React was the most significant and influential open source development in frontend technology in recent memory. Its growth beyond the web and its application in the realm of mobile development through React Native is both a testament to its popularity and a boon to its potential utility.

React Native is a library for creating native mobile applications using familiar web technologies that is built on top of React. What this means is that in order to understand React Native, we must first explore React. In this chapter, we'll examine the fundamentals of React. First, we'll talk briefly about the circumstances that led to React being created. We'll also cover these React concepts:

JSX, a JavaScript/HTML hybrid that we use to describe React components

React components

Component composition

Component properties, or props

Handling events

Component state

The React component lifecycle

Alternate component forms

Note

A note to the reader: this chapter focuses on React for the web, the original purpose of the library. This provides important context for the remainder of the book. If you already know React for the web, then it is probably safe to skip this chapter and proceed to Chapter 2, Saying Hello World in React Native.

Library versus framework

When people describe React, they often eschew the description of framework-a description often used for something such as Backbone or Angular-in favor of library. The reason for this more lightweight description is that React is not a complete solution for application development. It is often relegated to only a view-layer solution, and that characterization is mostly correct. React has some mechanisms for maintaining internal state, but it has no opinion about or solutions for data flow and management, server communication, routing, or other common frontend application concerns.

React, therefore, is often coupled with some other library or libraries to create a fully fleshed out application. The most common pairing is with an application architecture that is also the brainchild of the wizards at Facebook called Flux. Flux is not a library in and of itself; it is a set of design patterns that have been implemented by many different libraries, which will be discussed in more depth in Chapter 5, Flux and Redux.

Motivation for React

React and the community, libraries, and patterns that surround it are very much a reaction (pun intended) to some of the most frustrating and prevalent issues that plague JavaScript applications as they grow in size and complexity. JavaScript was not designed for creating large applications; it was designed, famously, in just 10 days as a scripting language to add a modicum of interactivity to lifeless web pages.

Chief among these concerns is the unpredictability that comes with shared mutable state. Historically, passing around JavaScript objects that represent the application's state to different views and controllers has been common practice. The ease with which those objects can be mutated by a rogue view, wisdom notwithstanding, can lead to hard-to-diagnose bugs, especially as applications and teams grow.

The foundational building block in a React application is the component, which is a declarative description of some visual feature on the page, such as a form or a menu. The declarative nature of components promotes predictability: given some set of external inputs (properties), the output is well defined and deterministic.

React also aims to combat one of the hurdles to writing efficient applications: the Document Object Model (DOM) is notoriously slow. If changes to the DOM are relatively infrequent, this may not be a problem, but in a complex application the time it takes to alter and redraw the DOM can add up. This is especially true for applications that take a declarative approach as React does, which necessitates re-rendering whenever the application's state changes.

The solution proposed by the React framework is to keep a representation of the DOM in memory, called a virtual DOM, and make all alterations there. Once the alterations have been made in memory, React can apply the minimum number of changes necessary to reconcile the real DOM with the virtual DOM. This also can allow quickly successive changes to be batched for greater efficiency. Taking this approach can lead to great gains in performance that can be noticed by end users.

In addition to solving some of the common problems faced when creating JavaScript applications, React components are modular and emphasize composition over inheritance, which makes code immensely reusable and testable. Additionally, a React component often has rendering logic, markup declaration, and even styles in the same file, which promotes the portability of code and the ability to write shared libraries of components.

Perhaps the most compelling reason to use React and React Native is the astounding amount of community adoption that has taken place in the last two years. People are excited about this technology, and rightly so; it is a novel approach to developing frontend applications that is, by most accounts, accelerating the development time on teams that choose to adopt it. With React Native, the idealistic promise of learn once, write anywhere is becoming more and more viable.

Getting started in React

To begin creating an interface in React, the first thing we need to do is break down the interface into conceptual components. We start with a large component, for instance, a news feed. We then say our large component is made up of, or composed of, other smaller components. In the case of our news feed, these smaller components might be individual news items. Each news item, in turn, might be composed of several even smaller components, such as images, a description,