Public and assets folders in Ruby on Rails - Mini Project: Build & Apply

Using Public and Assets Folders in Rails

📖 Scenario: You are building a simple Rails web app that needs to serve a custom logo image and a CSS file for styling. You will organize these files properly using the public and app/assets folders.

🎯 Goal: Create a Rails project structure where a logo image is placed in the public folder for direct access, and a CSS file is placed in the app/assets/stylesheets folder to style the homepage.

📋 What You'll Learn

Place a logo image file named logo.png inside the public/images folder

Create a CSS file named home.css inside app/assets/stylesheets

Add a CSS rule in home.css to set the background color of the body to #f0f0f0

Reference the logo image in the homepage view using the correct path to the public folder

Include the home.css stylesheet in the homepage layout

💡 Why This Matters

🌍 Real World

Web developers often need to organize images, stylesheets, and scripts properly in Rails projects to ensure efficient loading and maintainability.

💼 Career

Understanding the public and assets folders is essential for Rails developers to manage static files and styles, a common task in web development jobs.

1

Create the logo image in the public folder

Create a folder named images inside the public folder and add a file named logo.png inside public/images.

Ruby on Rails

# Create the folder public/images and add logo.png inside it
# Your code here

Hint

In Rails, files in the public folder are served directly. Place your image inside public/images.

2

Create the CSS file in assets

Create a CSS file named home.css inside app/assets/stylesheets.

Ruby on Rails

# Create app/assets/stylesheets/home.css
# Your code here

Hint

Use a text editor to create home.css and add a CSS rule for the body background color.

3

Reference the logo image in the homepage view

In the homepage view file app/views/home/index.html.erb, add an <img> tag that references the logo image using the path /images/logo.png.

Ruby on Rails

 tag referencing /images/logo.png in app/views/home/index.html.erb -->
# Your code here

Hint

Use the src attribute with the path starting with /images/ to access files in the public folder.

4

Include the CSS file in the homepage layout

In the homepage layout file app/views/layouts/application.html.erb, add a stylesheet link tag to include home.css using the Rails helper stylesheet_link_tag.

Ruby on Rails

# Your code here

Hint

Use <%= stylesheet_link_tag "home", media: "all" %> inside the <head> section to include your CSS file.

Practice

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

easy

A. To store static files served directly without processing

B. To hold Ruby code files for controllers and models

C. To keep database migration files

D. To store files that Rails compiles before sending

Solution

1. Step 1: Understand the role of the public folder

   The public folder contains files like images, HTML, or JavaScript that Rails serves directly to the browser without any processing.

2. Step 2: Compare with other folders

   The assets folder is for files Rails processes (like compiling CSS or JavaScript), so it is not the public folder's role.

3. Final Answer:

   To store static files served directly without processing -> Option A

4. Quick Check:

   Public folder = static files served directly [OK]

Hint: Public folder serves files as-is, no processing needed [OK]

Common Mistakes:

• Confusing public with assets folder
• Thinking public holds Ruby code
• Assuming public processes files before serving

2. Which of the following is the correct path to place a CSS file that Rails will precompile and serve?

easy

A. app/public/stylesheets/style.css

B. public/assets/stylesheets/style.css

C. app/assets/stylesheets/style.css

D. config/assets/stylesheets/style.css

Solution

1. Step 1: Identify the standard assets folder for stylesheets

   Rails expects CSS files to be inside app/assets/stylesheets for precompilation and processing.

2. Step 2: Eliminate incorrect paths

   The public folder is for static files, not processed assets. The config folder does not hold assets.

3. Final Answer:

   app/assets/stylesheets/style.css -> Option C

4. Quick Check:

   CSS in assets/stylesheets = app/assets/stylesheets/style.css [OK]

Hint: Assets folder is inside app/, not public or config [OK]

Common Mistakes:

• Placing CSS directly in public folder
• Using wrong folder like config/assets
• Confusing assets with public folder paths

3. Given a file logo.png placed inside public/images, what URL path will serve this image in a Rails app?

medium

A. /assets/images/logo.png

B. /public/images/logo.png

C. /app/assets/images/logo.png

D. /images/logo.png

Solution

1. Step 1: Understand how public folder maps to URL

   Files inside public are served from the root URL path. So public/images/logo.png is accessible at /images/logo.png.

2. Step 2: Eliminate other options

   /assets/images/logo.png is for assets pipeline files, not public. /public/images/logo.png and /app/assets/images/logo.png are not valid URL paths.

3. Final Answer:

   /images/logo.png -> Option D

4. Quick Check:

   Public folder maps directly to root URL [OK]

Hint: Public folder files appear at root URL path [OK]

Common Mistakes:

• Using /assets prefix for public files
• Including 'public' in URL path
• Confusing assets and public URL paths

4. You placed a JavaScript file in app/assets/javascripts but it is not loading in your Rails app. What is a likely cause?

medium

A. You forgot to include the JavaScript pack or manifest in your layout

B. The file is missing from the public folder

C. JavaScript files must be placed in public/javascripts

D. Rails does not support JavaScript in assets folder

Solution

1. Step 1: Check how assets are loaded in Rails

   Files in app/assets/javascripts need to be referenced in your layout via a manifest or pack tag to load properly.

2. Step 2: Eliminate incorrect causes

   JavaScript files do not belong in public for processing. Rails fully supports JavaScript in assets folder.

3. Final Answer:

   You forgot to include the JavaScript pack or manifest in your layout -> Option A

4. Quick Check:

   Assets must be linked in layout to load [OK]

Hint: Always include asset manifests or packs in your layout [OK]

Common Mistakes:

• Expecting assets to load without linking in layout
• Placing JS files in wrong folders
• Thinking public folder is for processed assets

5. You want to add a favicon to your Rails app that loads instantly without asset pipeline processing. Where should you place the favicon file and how should you reference it in your HTML?

hard

A. Place in app/assets/images and use <%= favicon_link_tag 'favicon.ico' %>

B. Place in public folder root and use <link rel='shortcut icon' href='/favicon.ico'>

C. Place in app/assets/images and use <link rel='icon' href='/assets/favicon.ico'>

D. Place in public/images and use <%= image_tag 'favicon.ico' %>

Solution

1. Step 1: Choose folder for instant loading without processing

   Files in public are served directly, so placing favicon.ico in public root ensures instant loading.

2. Step 2: Reference favicon correctly in HTML

   Use a standard HTML <link> tag with href pointing to /favicon.ico for browsers to find it.

3. Final Answer:

   Place in public folder root and use <link rel='shortcut icon' href='/favicon.ico'> -> Option B

4. Quick Check:

   Favicon in public root + direct link = Place in public folder root and use <link rel='shortcut icon' href='/favicon.ico'> [OK]

Hint: Put favicon in public root and link with standard HTML tag [OK]

Common Mistakes:

• Placing favicon in assets and expecting instant load
• Using image_tag instead of link tag for favicon
• Referencing wrong URL path for favicon