Rails new project generation - Cheat Sheet & Quick Revision

Recall & Review

beginner

What command do you use to create a new Rails project?

You use rails new project_name to create a new Rails project folder with all necessary files.

beginner

What does the rails new command generate?

It generates a new folder with a basic Rails app structure including folders like app, config, db, and files like Gemfile and config.ru.

intermediate

How can you create a new Rails project without installing all gems immediately?

Add the --skip-bundle option: rails new project_name --skip-bundle. This skips running bundle install after project creation.

intermediate

What option do you use with rails new to skip generating test files?

Use --skip-test to avoid creating test files when generating a new Rails project.

beginner

Why is it important to run bundle install after creating a new Rails project?

Because it installs all the Ruby gems your Rails app needs to work properly, like Rails itself and other libraries.

Which command creates a new Rails project named 'blog'?

A rails init blog

B rails create blog

C rails start blog

D rails new blog

The correct command to create a new Rails project is rails new project_name.

What folder does Rails create to hold your app's models, views, and controllers?

A lib

B public

C app

D bin

The app folder contains models, views, and controllers in a Rails project.

How do you skip running bundle install when creating a new Rails project?

A --skip-gem

B --skip-bundle

C --no-install

D --no-bundle

Use --skip-bundle to skip running bundle install after project creation.

Which file lists all the Ruby gems your Rails app needs?

A Gemfile

B config.ru

C routes.rb

D database.yml

The Gemfile lists all gems required by your Rails app.

What command installs all gems listed in the Gemfile?

A bundle install

B rails install

C gem install

D rails bundle

The bundle install command installs all gems listed in the Gemfile.

Explain the steps and command to create a new Rails project and prepare it for development.

Think about the command and what happens after running it.

Describe the purpose of the Gemfile in a new Rails project.

It controls what external code your app uses.

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