Rails new project generation - Practice Problems & Coding Challenges

Challenge - 5 Problems

📝 Syntax

intermediate

Correct command to create a new Rails project with PostgreSQL

Which command correctly creates a new Rails project named blog_app using PostgreSQL as the database?

A rails new blog_app --database=postgresql

B rails new blog_app -d mysql

C rails new blog_app --database=mysql

D rails new blog_app --db=postgresql

💡 Hint

Use the official Rails option to specify the database type.

The correct flag to specify the database is --database or -d followed by the database name. PostgreSQL is specified as 'postgresql'.

❓ component_behavior

intermediate

Effect of --skip-bundle option during Rails project creation

What happens when you run rails new shop_app --skip-bundle?

A The project is created but gems are not installed automatically.

B The project creation fails due to missing gems.

C The project is created and gems are installed automatically.

D The project is created without generating any files.

💡 Hint

Think about what 'bundle' means in Rails context.

The --skip-bundle option tells Rails to create the project but skip running 'bundle install' which installs gems.

❓ state_output

advanced

Number of files generated by default in a new Rails project

After running rails new forum_app with default options, how many files are generated in the project directory (approximately)?

A About 50 files

B About 100 files

C About 200 files

D About 500 files

💡 Hint

Rails generates many configuration, initializers, and default files.

A new Rails project generates roughly 200 files including config, app, bin, and test folders.

🔧 Debug

advanced

Error caused by missing Ruby version during Rails new

You run rails new api_app but get an error: Could not find Ruby version 3.1.0. What is the most likely cause?

A The command syntax is incorrect.

B Rails does not support Ruby 3.1.0.

C You need to update Rails to the latest version.

D Ruby 3.1.0 is not installed on your system.

💡 Hint

Rails requires the Ruby version specified in the Gemfile or default.

The error means your system does not have the Ruby version required by Rails or the project.

🧠 Conceptual

expert

Understanding the purpose of the Rails 'app' directory after new project generation

What is the main purpose of the app directory created by rails new?

A It stores configuration files for the Rails environment.

B It contains the core application code like models, views, and controllers.

C It holds the database schema and migration files.

D It contains the Ruby gems and dependencies.

💡 Hint

Think about where you write your app's main code.

The app directory is where Rails expects your main application code: models, views, controllers, helpers, and assets.

Practice

1. What does the rails new command do when creating a new project?

easy

A. It only installs Rails without creating any files.

B. It creates a new Rails app with all necessary files and folders.

C. It deletes old Rails projects from your computer.

D. It updates an existing Rails app to the latest version.

Solution

1. Step 1: Understand the purpose of rails new

   This command is designed to set up a new Rails application by creating all the needed files and folders automatically.

2. Step 2: Compare options

   Options A, C, and D describe actions unrelated to creating a new project. Only It creates a new Rails app with all necessary files and folders. correctly describes the creation of a new app with files.

3. Final Answer:

   It creates a new Rails app with all necessary files and folders. -> Option B

4. Quick Check:

   rails new creates app files = B [OK]

Hint: Remember: rails new sets up a full app folder [OK]

Common Mistakes:

• Thinking it only installs Rails without files
• Confusing it with update or delete commands
• Assuming it modifies existing projects

2. Which of the following is the correct syntax to create a new Rails project named blog with PostgreSQL as the database?

easy

A. rails new blog -d mysql

B. rails create blog --db=postgresql

C. rails generate blog --database=postgresql

D. rails new blog --database=postgresql

Solution

1. Step 1: Identify the correct command for new project creation

   The command to create a new Rails app is rails new, not rails create or rails generate.

2. Step 2: Check the database option syntax

   The correct option to specify the database is --database=postgresql. rails new blog -d mysql uses -d mysql which is for MySQL, not PostgreSQL.

3. Final Answer:

   rails new blog --database=postgresql -> Option D

4. Quick Check:

   Use rails new with --database= option = C [OK]

Hint: Use rails new appname --database=postgresql for PostgreSQL [OK]

Common Mistakes:

• Using rails create instead of rails new
• Wrong database option like -d mysql for PostgreSQL
• Confusing rails generate with project creation

3. After running rails new shop, which folder will NOT be created inside the new shop directory?

medium

A. app

B. bin

C. node_modules

D. config

Solution

1. Step 1: Recall default folders created by rails new

   Rails creates folders like app, bin, and config by default for app code, executables, and configuration.

2. Step 2: Understand node_modules folder creation

   The node_modules folder is created only after installing JavaScript packages with tools like Yarn or npm, not by default with rails new.

3. Final Answer:

   node_modules -> Option C

4. Quick Check:

   node_modules appears after JS install, not on new app [OK]

Hint: Default Rails folders exclude node_modules until JS packages installed [OK]

Common Mistakes:

• Assuming node_modules is created by default
• Confusing bin with temporary folders
• Not knowing which folders Rails generates automatically

4. You ran rails new myapp --database=sqlite3 but got an error saying the database adapter is missing. What is the most likely cause?

medium

A. You forgot to install the SQLite3 gem before creating the project.

B. The command rails new does not support SQLite3 database.

C. You must use --db=sqlite3 instead of --database=sqlite3.

D. You need to create the database manually before running rails new.

Solution

1. Step 1: Understand the error cause

   The error about missing database adapter usually means the required gem (SQLite3) is not installed on the system.

2. Step 2: Check command and options validity

   The rails new command supports SQLite3 by default with --database=sqlite3. The option --db= is invalid, and manual DB creation is not needed before project creation.

3. Final Answer:

   You forgot to install the SQLite3 gem before creating the project. -> Option A

4. Quick Check:

   Missing DB adapter error = missing gem install [OK]

Hint: Install DB gems before rails new to avoid adapter errors [OK]

Common Mistakes:

• Using wrong option --db= instead of --database=
• Thinking rails new can't use SQLite3
• Trying to create DB manually before project

5. You want to create a new Rails project named portfolio with PostgreSQL and skip the default test framework. Which command should you use?

hard

A. rails new portfolio --database=postgresql --skip-test

B. rails new portfolio -d postgresql --skip-test-framework

C. rails new portfolio --database=postgresql --skip-test-framework

D. rails new portfolio -d postgresql --skip-test

Solution

1. Step 1: Identify correct database option

   The shorthand for --database is -d, but both -d postgresql and --database=postgresql are valid.

2. Step 2: Identify correct option to skip test framework

   The correct option to skip the default test framework is --skip-test. The option --skip-test-framework is invalid.

3. Step 3: Combine correct options

   Both rails new portfolio -d postgresql --skip-test and rails new portfolio --database=postgresql --skip-test are valid, but the official documentation prefers the full option --database= with --skip-test.

4. Final Answer:

   rails new portfolio --database=postgresql --skip-test -> Option A

5. Quick Check:

   Use --database= for DB and --skip-test to skip tests [OK]

Hint: Use --database= for DB and --skip-test to skip tests [OK]

Common Mistakes:

• Using invalid option --skip-test-framework
• Using shorthand -d with wrong skip option
• Mixing shorthand and wrong skip flags