Course 37 - Building Web Apps with Ruby On Rails | Episode 16:Templates and Partials for Modular Rails APIs

In this lesson, you’ll learn about: modular JSON generation, JBuilder templates, and reusable API response structures1. The Problem with as_jsonUsing Ruby on Rails default serialization:🔹 Issue:Models become bloated with formatting logicBusiness logic + presentation logic get mixed🔹 Example problem:def as_json super.merge(custom_data: ...) end 👉 Key InsightModels should handle data, not how data is presented2. Introducing JBuilderUsing JBuilder:🔹 What it does:Moves JSON generation into view templatesKeeps controllers and models clean🔹 File structure:app/views/projects/show.json.jbuilder 👉 Key InsightJBuilder brings the MVC pattern back to balance3. JBuilder Template Basics🔹 Example:json.id @project.id json.project_title @project.title json.description @project.description 🔹 Features:Rename fieldsSelect attributesBuild structured JSON👉 Key InsightYou explicitly control every field in the response4. Handling Nested Associations🔹 Example:json.milestones @project.milestones do |milestone| json.id milestone.id json.name milestone.name end 👉 Key InsightJBuilder makes nested data easy and readable5. Adding Derived Data🔹 Example:json.single_day_project @project.start_date == @project.end_date 🔹 Use cases:FlagsCalculationsBusiness logic outputs👉 Key InsightYou can enrich API responses without touching the model6. Why JBuilder Is Better Than as_json🔹 With as_json:Logic scattered across modelsHard to maintain🔹 With JBuilder:Centralized JSON structureCleaner, modular design👉 Key InsightSeparation of concerns improves scalability7. JBuilder Partials (Reusability)🔹 Problem:Repeating the same JSON structure🔹 Solution:Use partialsjson.partial! "milestones/milestone", milestone: milestone 👉 Key InsightWrite once → reuse everywhere8. Creating a Partial🔹 File:app/views/milestones/_milestone.json.jbuilder 🔹 Example:json.id milestone.id json.name milestone.name 👉 Key InsightPartials act like reusable components for JSON9. Benefits of Partials🔹 Advantages:Consistency across endpointsEasy updatesReduced duplication👉 Key InsightChange in one place → updates everywhere10. Clean API Architecture with JBuilder🔹 Controller:render :show 🔹 View (JBuilder):Handles full JSON structure🔹 Model:Only business logic👉 Key InsightEach layer has a single responsibilityKey TakeawaysAvoid overloading models with as_jsonUse JBuilder for structured, readable JSONTemplates control formattingPartials eliminate duplicationImproves maintainability and scalabilityYou can listen and download our episodes for free on more than 10 different platforms:https://linktr.ee/cybercode_academy