Rails Action Controllers

Master HTTP request handling with Action Controller, building RESTful endpoints, managing request/response cycles, implementing authentication, and handling callbacks.

When to Use This Skill

• Building REST API endpoints or web controllers
• Handling HTTP requests, parameters, and responses
• Implementing authentication and authorization filters
• Managing cookies, sessions, and flash messages
• Working with routing, URL parameters, and path helpers
• Handling errors and exceptions in controller actions
• Building both JSON API and HTML template responses
• Implementing before/after/around action callbacks

Quick Start

Build RESTful controllers with proper action structure, parameter handling, and request lifecycle management.

Quick Start

Generate a controller:

rails generate controller Posts index show create update destroy

Create a controller:

class PostsController < ApplicationController
  before_action :authenticate_user!
  before_action :set_post, only: [:show, :update, :destroy]
  
  def index
    @posts = Post.all
    render json: @posts
  end
  
  def show
    render json: @post
  end
  
  def create
    @post = Post.new(post_params)
    if @post.save
      render json: @post, status: :created
    else
      render json: @post.errors, status: :unprocessable_entity
    end
  end
  
  private
  
  def set_post
    @post = Post.find(params[:id])
  end
  
  def post_params
    params.require(:post).permit(:title, :content)
  end
end

Core Topics

Routing & Parameters: See routing-params.md for RESTful routing, nested resources, and params handling.

Filters & Callbacks: See filters-callbacks.md for before/after actions, authentication, authorization, and exception handling.

Patterns: See patterns.md for request lifecycle, strong parameters, error handling, and JSON/HTML responses.

Sessions & Cookies: See references/sessions-cookies.md for session management, flash messages, and cookie handling (signed, encrypted, permanent).

Advanced Authentication: See references/authentication-advanced.md for HTTP authentication, token-based auth, JWT, OAuth 2.0, and error handling with rescue_from.

Streaming & Downloads: See references/streaming-downloads.md for file downloads, uploads, streaming responses, and Server-Sent Events.

Scripts

REST Controller Scaffold: scripts/rest-controller-scaffold.sh generates a complete REST controller with CRUD actions.

API Controller Template: scripts/api-controller-template.sh generates an API-only controller with authentication and error handling.

Examples

See examples.md for:

• Full CRUD controller implementation
• Nested resource controllers
• API vs HTML rendering
• Error handling and status codes