Course 37 - Building Web Apps with Ruby On Rails | Episode 15: Multi-format Controllers and Custom JSON Serialization

In this lesson, you’ll learn about: multi-format responses, JSON serialization, and building clean, reusable Rails API controllers1. Multi-Format Controller ResponsesUsing Ruby on Rails:🔹 Problem:Different clients need different formatsBrowser → HTMLMobile app → JSONExternal systems → XML🔹 Solution:Use respond_todef show @user = User.find(params[:id]) respond_to do |format| format.html format.json { render json: @user } format.xml { render xml: @user } end end 👉 Key InsightOne controller action can serve multiple clients efficiently2. How Clients Choose the Format🔹 Methods:HTTP Accept headerURL extension (.json, .xml)🔹 Example:GET /users/1.json 👉 Key InsightThe client—not the server—decides the response format3. The Serialization Pipeline🔹 Step 1: Data PreparationConvert model → Ruby hash🔹 Step 2: Data TransformationConvert hash → JSON string👉 Key InsightSerialization is a two-step process, not a single action4. as_json vs to_json🔹 as_json:Returns a Ruby hashUsed for customization🔹 to_json:Converts to JSON string🔹 Best practice:render json: @user 👉 Key InsightLet Rails handle conversion to avoid double encoding5. Why Use render Instead of Manual Conversion❌ Bad:render json: @user.to_json ✅ Good:render json: @user 👉 Key InsightRails automatically calls serialization methods correctly6. Moving Logic from Controllers to Models🔹 Problem:Controllers become cluttered🔹 Solution:Customize JSON in the modeldef as_json(options = {}) super(only: [:id, :name]) end 👉 Key InsightFat models + skinny controllers = clean architecture7. Filtering Data for Efficiency🔹 Options:only → include specific fieldsexcept → exclude fieldsrender json: @user, only: [:id, :email] 👉 Key InsightSend only what the client needs → better performance8. Including Associations🔹 Example:render json: @user, include: :posts 👉 Key InsightYou can return related data in a single response9. Renaming and Customizing Fields🔹 Example:def as_json(options = {}) super.merge({ full_name: "#{first_name} #{last_name}" }) end 👉 Key InsightAPIs should be client-friendly, not database-driven10. Adding Derived Data🔹 Examples:Unix timestampsBoolean flagsComputed valuesdef as_json(options = {}) super.merge({ created_at_unix: created_at.to_i, active: status == "active" }) end 👉 Key InsightAPIs can provide ready-to-use data, not raw data11. Clean Architecture Strategy🔹 Controller:Handles request/response🔹 Model:Handles data formatting👉 Key InsightSeparation of concerns improves maintainabilityKey TakeawaysUse respond_to for multi-format APIsSerialization = prepare + transformPrefer render json: over manual conversionMove formatting logic into modelsCustomize responses for performance and clarityBig PictureYou are building:👉 Flexible APIs for multiple clients👉 Efficient data responses👉 Clean, maintainable Rails architectureMental ModelRequest → controller action → choose format → model prepares data → Rails serializes → response sentYou can listen and download our episodes for free on more than 10 different platforms:https://linktr.ee/cybercode_academy