Convention over configuration principle in Ruby on Rails - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Rails Naming Conventions

In Rails, which file name will Rails automatically associate with the UsersController class following the convention over configuration principle?

A users_controller.rb

B UsersController.rb

C user_controller.rb

D userscontroller.rb

💡 Hint

Think about how Rails expects controller files to be named in snake_case matching the controller class name.

Rails expects controller files to be named in snake_case matching the controller class name. For UsersController, the file should be users_controller.rb. This is a key example of convention over configuration.

❓ component_behavior

intermediate

Default Database Table Name for a Model

Given a Rails model class named ProductCategory, what is the default database table name Rails will use without any configuration?

A product_categories

B productcategory

C product_category

D ProductCategories

💡 Hint

Rails pluralizes and snake_cases model class names to get table names.

Rails automatically converts model class names from CamelCase to snake_case and pluralizes them to get the table name. So ProductCategory becomes product_categories.

📝 Syntax

advanced

Identifying the Correct Route Helper Method

In a Rails app with a resource declared as resources :orders, which helper method will generate the path to the new order form following Rails conventions?

A order_new_path

B create_order_path

C new_order_path

D orders_new_path

💡 Hint

Rails uses a specific pattern for new resource routes: new__path.

Rails generates route helper methods based on resource names. For the new form of orders, the helper is new_order_path.

🔧 Debug

advanced

Why Does This Rails View Template Not Render?

You have a controller named ArticlesController. You created a view template named show.html.erb inside the folder app/views/article. Why does Rails not render this template by default?

A The template file should be named show.html.html

B Rails requires the template to be in app/views/shared

C The controller name should be ArticleController

D The folder name should be plural: app/views/articles

💡 Hint

Check the folder naming convention for views matching controller names.

Rails expects the view folder to be the pluralized form of the controller name. Since the controller is ArticlesController, the folder must be articles, not article.

❓ state_output

expert

Effect of Skipping Convention in Model Associations

Consider these two Rails models:

class User < ApplicationRecord
has_many :posts
end

class Post < ApplicationRecord
belongs_to :author, class_name: 'User'
end

What will happen if you try to access post.author without specifying the foreign key in the Post model, assuming the posts table has a user_id column?

A Rails will use user_id automatically for author association

B Rails will raise an error because it expects author_id column by default

C Rails will return nil because the association is not configured properly

D Rails will correctly find the user because of class_name and user_id column

💡 Hint

Think about how Rails infers foreign keys from association names.

When you use belongs_to :author, class_name: 'User', Rails expects a foreign key named author_id by default. Since the table has user_id instead, Rails cannot find the association without specifying foreign_key: 'user_id'.

Practice

1. What does the Convention over configuration principle in Rails primarily help with?

easy

A. Automatically generating user interface designs

B. Reducing the amount of setup code by following naming rules

C. Making Rails apps run faster by optimizing queries

D. Forcing developers to write detailed configuration files

Solution

1. Step 1: Understand the principle's goal

   Convention over configuration means Rails guesses what you want if you follow its naming rules.

2. Step 2: Identify the main benefit

   This reduces the need to write extra setup or configuration code manually.

3. Final Answer:

   Reducing the amount of setup code by following naming rules -> Option B

4. Quick Check:

   Convention over configuration = less setup code [OK]

Hint: Think: Rails guesses if you follow rules, so less setup [OK]

Common Mistakes:

• Confusing it with performance optimization
• Thinking it forces more configuration files
• Assuming it auto-generates UI designs

2. Which of the following is the correct Rails convention for naming a model class representing users?

easy

A. class User < ApplicationRecord

B. class users < ApplicationRecord

C. class user < ApplicationRecord

D. class USER < ApplicationRecord

Solution

1. Step 1: Recall Rails naming conventions for models

   Model class names are singular and start with a capital letter, e.g., User.

2. Step 2: Check syntax correctness

   class User < ApplicationRecord uses correct class name capitalization and inherits from ApplicationRecord.

3. Final Answer:

   class User < ApplicationRecord -> Option A

4. Quick Check:

   Model class names are singular and capitalized [OK]

Hint: Model names are singular and capitalized classes [OK]

Common Mistakes:

• Using plural or lowercase class names
• Not capitalizing the class name
• Using all uppercase letters

3. Given a Rails model named Article, which database table name will Rails expect by convention?

medium

A. articles

B. article

C. Article

D. article_table

Solution

1. Step 1: Recall Rails table naming convention

   Rails expects database tables to be plural lowercase versions of model names.

2. Step 2: Apply to the model 'Article'

   The plural lowercase form is 'articles'.

3. Final Answer:

   articles -> Option A

4. Quick Check:

   Model 'Article' maps to table 'articles' [OK]

Hint: Model name pluralized lowercase = table name [OK]

Common Mistakes:

• Using singular table names
• Using capitalized table names
• Adding extra suffixes like '_table'

4. You created a model class class Person < ApplicationRecord but named the database table people_data. What is the main issue here?

medium

A. Rails will use the people_data table without problems

B. Rails will automatically find the table despite the name difference

C. Rails will raise an error because the table name does not follow convention

D. Rails will ignore the model and use a default table

Solution

1. Step 1: Understand default table naming

   Rails expects the table name to be the plural form of the model name, here 'people'.

2. Step 2: Check mismatch impact

   Since the table is named 'people_data', Rails won't find it automatically and will raise an error unless explicitly told.

3. Final Answer:

   Rails will raise an error because the table name does not follow convention -> Option C

4. Quick Check:

   Table name mismatch causes error unless configured [OK]

Hint: Table name must match plural model name or configure explicitly [OK]

Common Mistakes:

• Assuming Rails guesses any table name
• Thinking Rails silently ignores the model
• Believing Rails auto-corrects table names

5. You want to create a Rails controller for managing blog posts. According to convention, which controller class name and file path are correct?

hard

A. class BlogPostController < ApplicationController in app/controllers/blog_post_controller.rb

B. class blogpostscontroller < ApplicationController in app/controllers/blogposts_controller.rb

C. class BlogPosts < ApplicationController in app/controllers/blog_posts.rb

D. class BlogPostsController < ApplicationController in app/controllers/blog_posts_controller.rb

Solution

1. Step 1: Recall controller naming conventions

   Controllers are plural, camel case with 'Controller' suffix, e.g., BlogPostsController.

2. Step 2: Recall file path conventions

   File names are snake_case plural with '_controller.rb' suffix, e.g., blog_posts_controller.rb.

3. Final Answer:

   class BlogPostsController < ApplicationController in app/controllers/blog_posts_controller.rb -> Option D

4. Quick Check:

   Controller class plural + Controller suffix, file snake_case plural [OK]

Hint: Controller class plural CamelCase + file snake_case plural_controller.rb [OK]

Common Mistakes:

• Using singular controller class names
• Incorrect file naming or casing
• Omitting 'Controller' suffix