First Rails application - Cheat Sheet & Quick Revision

Recall & Review

beginner

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

You use rails new app_name to create a new Rails application, where app_name is your project folder name.

beginner

What file runs the Rails server to see your app in a browser?

You run rails server or rails s in your app folder to start the server. Then visit http://localhost:3000 in your browser.

beginner

What is the purpose of the app/views folder in a Rails app?

The app/views folder holds the HTML templates that show the user interface. Rails fills these templates with data to display pages.

beginner

What does MVC stand for in Rails?

MVC means Model-View-Controller. It's a way Rails organizes code: Models handle data, Views show pages, Controllers manage requests.

beginner

How do you generate a new controller in Rails?

Use rails generate controller ControllerName to create a new controller and its view files.

Which command starts the Rails server?

A rails server

B rails start

C rails run

D rails begin

The correct command to start the Rails server is rails server or rails s.

Where do you put HTML templates in a Rails app?

A app/models

B app/controllers

C app/views

D app/assets

HTML templates go inside app/views to show pages to users.

What does MVC stand for?

A Module-View-Controller

B Model-View-Controller

C Model-Visual-Component

D Main-View-Code

MVC stands for Model-View-Controller, the design pattern Rails uses.

How do you create a new Rails app named 'blog'?

A rails create blog

B rails start blog

C rails init blog

D rails new blog

Use rails new blog to create a new Rails app called 'blog'.

Which folder contains the code that handles user requests?

A app/controllers

B app/models

C app/views

D config

Controllers in app/controllers handle user requests and decide what to do.

Explain the steps to create and run your first Rails application.

Think about commands and what you do to see your app in a browser.

Describe the MVC pattern and how Rails uses it in your first app.

Imagine a restaurant: who cooks, who serves, who takes orders?

Practice

1. What command do you use to create a new Rails application folder?

easy

A. rails init myapp

B. rails new myapp

C. rails create myapp

D. rails start myapp

Solution

1. Step 1: Understand Rails app creation command

   The official command to create a new Rails app is rails new followed by the app name.

2. Step 2: Match the command with options

   Only rails new myapp uses rails new myapp, which is correct syntax.

3. Final Answer:

   rails new myapp -> Option B

4. Quick Check:

   Create app folder = rails new [OK]

Hint: Remember: 'rails new' creates the app folder [OK]

Common Mistakes:

• Using 'rails start' instead of 'rails new'
• Confusing 'rails create' with 'rails new'
• Trying 'rails init' which is not a Rails command

2. Which command starts the Rails server so you can view your app in a browser?

easy

A. rails launch

B. rails start

C. rails run

D. rails server

Solution

1. Step 1: Identify the command to run the Rails server

   The correct command to start the Rails server is rails server.

2. Step 2: Compare with options

   Only rails server matches the correct command exactly.

3. Final Answer:

   rails server -> Option D

4. Quick Check:

   Start server = rails server [OK]

Hint: Use 'rails server' to launch your app locally [OK]

Common Mistakes:

• Typing 'rails start' which is invalid
• Using 'rails run' which does not start the server
• Trying 'rails launch' which is not a Rails command

3. What will happen if you run rails new blog and then cd blog followed by rails server?

medium

A. A new Rails app named 'blog' is created and the server starts to serve it locally.

B. An error occurs because 'rails server' must be run before 'rails new'.

C. The server starts but shows a blank page because no views are created yet.

D. The command fails because 'cd blog' is not a valid Rails command.

Solution

1. Step 1: Understand the sequence of commands

   rails new blog creates a new app folder named 'blog'. cd blog moves into that folder. rails server starts the server for that app.

2. Step 2: Analyze the expected behavior

   Running these commands in order creates the app and starts the server correctly, serving the default Rails welcome page.

3. Final Answer:

   A new Rails app named 'blog' is created and the server starts to serve it locally. -> Option A

4. Quick Check:

   rails new + cd + rails server = app runs [OK]

Hint: Create app, enter folder, then start server to see app [OK]

Common Mistakes:

• Thinking 'rails server' must run before app creation
• Assuming 'cd blog' is a Rails command instead of shell
• Expecting an error when running these commands in order

4. You ran rails new myapp but when you try rails server inside the folder, you get an error. What is the most likely cause?

medium

A. You must create a controller before starting the server.

B. You need to run rails start instead of rails server.

C. You forgot to run bundle install to install dependencies.

D. The folder name 'myapp' is invalid for Rails apps.

Solution

1. Step 1: Identify common setup step after creating app

   After rails new, you usually run bundle install to install gems needed by the app.

2. Step 2: Understand error cause

   If dependencies are missing, rails server will fail to start due to missing gems.

3. Final Answer:

   You forgot to run bundle install to install dependencies. -> Option C

4. Quick Check:

   Missing gems? Run bundle install first [OK]

Hint: Run 'bundle install' after 'rails new' before starting server [OK]

Common Mistakes:

• Trying 'rails start' which is invalid
• Thinking a controller is required before server start
• Believing folder name causes the error

5. You want to create a new Rails app named shop and immediately start the server. Which sequence of commands is correct?

hard

A. rails new shop -> cd shop -> rails server

B. rails create shop -> rails server

C. rails new shop -> rails server

D. cd shop -> rails new shop -> rails server

Solution

1. Step 1: Create the app folder with correct command

   Use rails new shop to create the app folder named 'shop'.

2. Step 2: Change directory into the new app folder

   Run cd shop to move into the app folder before starting the server.

3. Step 3: Start the Rails server inside the app folder

   Run rails server to launch the app locally.

4. Final Answer:

   rails new shop -> cd shop -> rails server -> Option A

5. Quick Check:

   Create app, enter folder, start server = correct order [OK]

Hint: Create app, cd into it, then run server [OK]

Common Mistakes:

• Skipping 'cd' before running server
• Using 'rails create' which is invalid
• Running server outside app folder