Foreword xiPreface xiiiAcknowledgments xxiAbout the Author xxiiiChapter 1: Introduction to Component-Based Rails Applications 11.1 Component-Based Rails 21.2 Benefits of Component-Based Applications 41.3 Component-Based Ruby 131.4 The Application Continuum 141.5 Related Works 15Chapter 2: Creating a Component-Based Application 172.1 The Entire App Inside a Component 182.2 ActiveRecord and Handling Migrations within Components 272.3 Handling Dependencies within Components 34Chapter 3: Tooling for Components 493.1 Testing a Component 503.2 Testing the Main Application 653.3 Asset Loading for Components 743.4 Switching Databases 823.5 Deploying to Platforms-as-a-Service 863.6 Updating Application Dependencies 903.7 Proposal for a Different Application Root—Showcasing the Difference of Components’ Structure 99Chapter 4: Component Refactorings: Extracting Components Out of Components 1114.1 Determining What to Extract: Bottom-Up 1124.2 Refactoring: Extract Domain Gem—Predictor 1204.3 Determining What to Extract: Top-Down 1394.4 Refactoring: Pulling Up a UI Component—TeamsAdmin, GamesAdmin, PredictionUI, WelcomeUI 1504.5 Refactoring: Pushing Down a Model Component—Teams, Games 1684.6 Refactoring: Improve Naming of Component—AppComponent to WebUI 1834.7 More Component Refactoring Patterns 189Chapter 5: From Ball of Mud to First Components 1955.1 Small Steps 1965.2 One Big Step 196Chapter 6: Component-Based Rails in Relation to Other Patterns 2116.1 Hexagonal Architecture 2126.2 Data-Context-Integration (DCI) 227Chapter 7: Components in Other Languages 2377.1 Kotlin, Java, and Gradle 2387.2 .NET / C 2417.3 Conclusion 243Appendix 245A.1 Plain versus --full versus --mountable Engines 245A.2 How Do Engine Routes and Engine Mounting Work? 254A.3 Additional Testing with Older Versions of Rails 261Index 265