Best Practices for Controller Design in Rails

1. Introduction

In this tutorial, we will explore the best practices for designing controllers in Rails. Our goal is to understand how to keep our controllers lean, meaning they should only be responsible for a minimal number of tasks such as handling user input and returning appropriate responses.

By the end of this tutorial, you will learn:

• The role of controllers in Rails
• How to design lean and efficient controllers
• Best practices for controller design

Prerequisites: Basic understanding of Rails architecture and MVC (Model-View-Controller) design pattern.

2. Step-by-Step Guide

2.1 Controller Responsibilities

In Rails, a controller is the component of the application that responds to external requests from the web server, interacting with the models and views to perform the requested operation. It should be as lean as possible, handling only user input and responses.

2.2 Best Practices

1. Single Responsibility Principle: Each controller action should have a single responsibility. For example, the create action should only be responsible for creating a resource.

class UsersController < ApplicationController
  def create
    @user = User.new(user_params)

    if @user.save
      redirect_to @user
    else
      render 'new'
    end
  end
end

In this example, the create action is only responsible for creating a new user. If the user is saved successfully, it redirects to the user page, otherwise, it renders the 'new' form again.

1. Keep business logic in models: Controllers should be kept slim and not handle business logic. Business logic should be in the model.

2. Use before actions: Before actions can be used to set up any instance variables that will be used in the action. This helps to keep your actions tidy and avoid repetition.

3. Don't repeat yourself (DRY): If you find yourself writing the same code in multiple places, consider moving it into a helper or use a before action.

3. Code Examples

Here is an example of a lean and efficient controller:

class UsersController < ApplicationController
  before_action :set_user, only: [:show, :edit, :update, :destroy]

  # GET /users
  def index
    @users = User.all
  end

  # GET /users/1
  def show
  end

  # GET /users/new
  def new
    @user = User.new
  end

  # GET /users/1/edit
  def edit
  end

  # POST /users
  def create
    @user = User.new(user_params)

    if @user.save
      redirect_to @user, notice: 'User was successfully created.'
    else
      render :new
    end
  end

  # PATCH/PUT /users/1
  def update
    if @user.update(user_params)
      redirect_to @user, notice: 'User was successfully updated.'
    else
      render :edit
    end
  end

  # DELETE /users/1
  def destroy
    @user.destroy
    redirect_to users_url, notice: 'User was successfully destroyed.'
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_user
      @user = User.find(params[:id])
    end

    # Only allow a list of trusted parameters through.
    def user_params
      params.require(:user).permit(:name, :email)
    end
end

4. Summary

In this tutorial, we've covered the best practices for designing controllers in Rails:

• Keeping controllers lean and efficient
• Single Responsibility Principle
• Moving business logic to models
• Using before actions
• DRY principle

To further your learning, you could read about RESTful design, additional Rails conventions, and other design patterns.

5. Practice Exercises

1. Exercise: Create a PostsController using the best practices we've just covered.

2. Exercise: Refactor an existing controller in your application to follow these best practices.

Solutions and explanations will depend on the specific controllers and applications, but remember to keep controllers lean, follow the Single Responsibility Principle, move business logic to models, use before actions, and don't repeat yourself.

Happy coding!