App folder organization in Ruby on Rails - Mini Project: Build & Apply

Organize a Rails App Folder

📖 Scenario: You are starting a new Ruby on Rails project for a simple blog website. To keep your project clean and easy to understand, you need to organize the main folders and files inside the app directory properly.

🎯 Goal: Learn how to create the basic folder structure inside the app folder of a Rails project, including models, views, and controllers folders, and add a simple Ruby file inside the models folder.

📋 What You'll Learn

Create the main folders inside the app directory: models, views, and controllers

Add a Ruby file named post.rb inside the models folder

Inside post.rb, define a class Post that inherits from ApplicationRecord

Create a configuration variable MAX_POSTS inside post.rb and set it to 10

Add a method self.max_posts inside the Post class that returns the value of MAX_POSTS

💡 Why This Matters

🌍 Real World

Organizing the app folder correctly is essential for Rails projects to keep code clean and maintainable. It helps developers find files quickly and follow Rails conventions.

💼 Career

Understanding Rails folder structure and how to create models, views, and controllers is a fundamental skill for Rails developers working on web applications.

1

Create the main folders inside app

Create three folders inside the app directory named models, views, and controllers.

Ruby on Rails

# Create folders: app/models, app/views, app/controllers
# Your code here

Hint

In your Rails project folder, create three new folders named exactly models, views, and controllers inside the app folder.

2

Add post.rb file with Post class

Inside the models folder, create a file named post.rb. In this file, define a class called Post that inherits from ApplicationRecord.

Ruby on Rails

# Inside app/models/post.rb
class Post < ApplicationRecord
  # Your code here
end

Hint

Define a Ruby class named Post that inherits from ApplicationRecord inside post.rb.

3

Add a configuration variable MAX_POSTS

Inside the Post class in post.rb, add a constant variable named MAX_POSTS and set it to 10.

Ruby on Rails

class Post < ApplicationRecord
  # Define MAX_POSTS constant here
  # Your code here
end

Hint

Inside the Post class, write MAX_POSTS = 10 to create a constant.

4

Add a class method self.max_posts returning MAX_POSTS

Inside the Post class in post.rb, add a class method named self.max_posts that returns the value of the constant MAX_POSTS.

Ruby on Rails

class Post < ApplicationRecord
  MAX_POSTS = 10
  # Define self.max_posts method here
  # Your code here
end

Hint

Define a class method self.max_posts that returns MAX_POSTS inside the Post class.

Practice

1. What is the main purpose of the app/ folder in a Rails application?

easy

A. To store database backups and logs

B. To hold static assets like images and stylesheets

C. To keep configuration files for the server

D. To organize the code by its role, like models, views, and controllers

Solution

1. Step 1: Understand the role of app/ folder

   The app/ folder is designed to organize the main parts of the Rails app code by their function.

2. Step 2: Identify what belongs in app/

   Models, views, and controllers are the core components stored in app/, not backups or static files.

3. Final Answer:

   To organize the code by its role, like models, views, and controllers -> Option D

4. Quick Check:

   App folder organizes code by role = B [OK]

Hint: Remember MVC parts live inside app/ folder [OK]

Common Mistakes:

• Confusing app/ with config/ or public/ folders
• Thinking assets like images go inside app/
• Assuming app/ holds database files

2. Which folder inside app/ should contain the code that responds to user requests?

easy

A. controllers

B. views

C. models

D. helpers

Solution

1. Step 1: Identify the role of controllers

   Controllers handle incoming user requests and decide what to do next.

2. Step 2: Match folder to role

   The controllers folder contains this code, while models manage data and views display content.

3. Final Answer:

   controllers -> Option A

4. Quick Check:

   Request handling = controllers = C [OK]

Hint: Controllers respond to requests inside app/ [OK]

Common Mistakes:

• Choosing models instead of controllers
• Confusing views with controllers
• Thinking helpers handle requests

3. Given this folder structure inside app/:
app/models/user.rb,
app/controllers/users_controller.rb,
app/views/users/index.html.erb
What is the role of users_controller.rb?

medium

A. It contains the HTML layout for user pages

B. It defines how user data is stored in the database

C. It manages the logic to handle user-related requests

D. It stores user session information

Solution

1. Step 1: Identify the controller file

   The file users_controller.rb is inside the controllers folder, so it handles requests.

2. Step 2: Understand controller responsibility

   Controllers manage logic for requests, not data storage or views.

3. Final Answer:

   It manages the logic to handle user-related requests -> Option C

4. Quick Check:

   Controller file handles requests = A [OK]

Hint: Controllers handle logic for requests, not data or views [OK]

Common Mistakes:

• Confusing controller with model responsibilities
• Thinking controller holds HTML templates
• Assuming controller stores session data

4. You accidentally put a view template file inside app/models/. What problem will this cause?

medium

A. The view will not render because Rails looks for templates only in app/views/

B. No problem; Rails loads views from any folder inside app/

C. The model will try to execute the view code causing a crash

D. Rails will raise an error because views must be in app/views/

Solution

1. Step 1: Understand Rails folder conventions

   Rails expects view templates only inside app/views/ to render them properly.

2. Step 2: Identify effect of wrong folder

   If a view is inside app/models/, Rails will not find it and won't render it.

3. Final Answer:

   The view will not render because Rails looks for templates only in app/views/ -> Option A

4. Quick Check:

   Views must be in app/views = D [OK]

Hint: Views only render from app/views folder [OK]

Common Mistakes:

• Expecting Rails to raise an error immediately
• Thinking models execute view code
• Assuming views load from anywhere in app/

5. You want to add a new feature that sends emails when a user signs up. Where should you place the mailer class in the Rails app/ folder structure?

hard

A. Inside app/controllers/ because it handles user actions

B. Inside app/mailers/ because mailers have their own folder

C. Inside app/models/ because it deals with user data

D. Inside app/views/ because emails have templates

Solution

1. Step 1: Recall Rails folder for mailers

   Rails has a dedicated app/mailers/ folder for mailer classes that send emails.

2. Step 2: Understand why mailers don't go elsewhere

   Controllers handle requests, models manage data, and views hold templates, but mailers have their own place.

3. Final Answer:

   Inside app/mailers/ because mailers have their own folder -> Option B

4. Quick Check:

   Mailers live in app/mailers = A [OK]

Hint: Put mailers in app/mailers folder [OK]

Common Mistakes:

• Placing mailers in controllers or models folders
• Confusing mailer classes with views
• Not knowing mailers have a separate folder