Environment configuration files in Ruby on Rails - Mini Project: Build & Apply

Environment Configuration Files in Rails

📖 Scenario: You are building a Rails web application that needs to behave differently in development and production. For example, you want to set a custom greeting message that changes based on the environment.

🎯 Goal: Create environment configuration files in a Rails app to store a greeting message. Then, access this message in the application code to display the correct greeting depending on the environment.

📋 What You'll Learn

Create a configuration file for the development environment with a greeting message

Create a configuration file for the production environment with a different greeting message

Add a configuration variable to access the greeting message

Use the configuration variable in a Rails controller to display the greeting

💡 Why This Matters

🌍 Real World

Rails apps often need different settings for development, testing, and production environments to behave correctly and securely.

💼 Career

Understanding environment configuration is essential for Rails developers to manage app behavior and deployment safely and efficiently.

1

Create development environment configuration file

Create a file named config/environments/development.rb and add a line to set config.greeting = 'Hello from Development!' inside the Rails.application.configure do ... end block.

Ruby on Rails

# Create config/environments/development.rb with greeting configuration
Rails.application.configure do
  # Your code here
end

Hint

Remember to put the greeting inside the Rails.application.configure do ... end block.

2

Create production environment configuration file

Create a file named config/environments/production.rb and add a line to set config.greeting = 'Welcome to Production!' inside the Rails.application.configure do ... end block.

Ruby on Rails

Rails.application.configure do
  config.greeting = 'Hello from Development!'
end

# Create config/environments/production.rb with greeting configuration
Rails.application.configure do
  # Your code here
end

Hint

Use the same structure as development.rb but with the production greeting.

3

Add configuration access in application controller

In app/controllers/application_controller.rb, add a method named greeting_message that returns Rails.configuration.greeting.

Ruby on Rails

Rails.application.configure do
  config.greeting = 'Hello from Development!'
end

Rails.application.configure do
  config.greeting = 'Welcome to Production!'
end

class ApplicationController < ActionController::Base
  # Your code here
end

Hint

Define a method that returns the greeting from Rails.configuration.

4

Use greeting message in a view

In app/views/layouts/application.html.erb, add a line inside the <body> tag to display the greeting message by calling greeting_message.

Ruby on Rails

Rails.application.configure do
  config.greeting = 'Hello from Development!'
end

Rails.application.configure do
  config.greeting = 'Welcome to Production!'
end

class ApplicationController 


  MyApp


  

Hint

Use ERB tags to call the greeting_message method inside the body.

Practice

1. What is the main purpose of environment configuration files in a Rails application?

easy

A. To set different settings for development, test, and production environments

B. To store user data securely

C. To define database schemas

D. To write application business logic

Solution

1. Step 1: Understand environment files role

   Environment files in Rails are used to configure how the app behaves in different situations like development or production.

2. Step 2: Match purpose to options

   Only To set different settings for development, test, and production environments describes setting different configurations for each environment, which is the main purpose.

3. Final Answer:

   To set different settings for development, test, and production environments -> Option A

4. Quick Check:

   Environment files configure settings per environment [OK]

Hint: Think: different setups for dev, test, prod [OK]

Common Mistakes:

• Confusing environment files with database schema files
• Thinking environment files store user data
• Assuming business logic is set here

2. Which file path correctly points to the production environment configuration in a Rails app?

easy

A. config/production/environment.rb

B. config/environments/production.rb

C. config/environment/production.rb

D. config/environments.rb/production

Solution

1. Step 1: Recall Rails environment file location

   Rails stores environment configs inside the config/environments directory.

2. Step 2: Identify correct file name for production

   The production environment file is named production.rb inside that folder.

3. Final Answer:

   config/environments/production.rb -> Option B

4. Quick Check:

   Production config file path = config/environments/production.rb [OK]

Hint: Look for config/environments/[env].rb [OK]

Common Mistakes:

• Swapping folder and file names
• Using incorrect folder order
• Adding extra file extensions

3. Given this code in config/environments/development.rb:

Rails.application.configure do
  config.cache_classes = false
  config.eager_load = false
end

What effect does this configuration have when running the app in development?

medium

A. Eager loading loads all code at startup, slowing boot time

B. Classes are cached, improving performance but requiring server restart

C. Classes reload on each request, speeding up development changes

D. Caching is enabled, so data is stored permanently

Solution

1. Step 1: Understand config.cache_classes = false

   This means Rails reloads classes on every request, so code changes show immediately without restarting.

2. Step 2: Understand config.eager_load = false

   Eager loading off means Rails does not load all code at startup, which is typical for development to save boot time.

3. Final Answer:

   Classes reload on each request, speeding up development changes -> Option C

4. Quick Check:

   cache_classes false means reload classes each request [OK]

Hint: cache_classes false means reload code on every request [OK]

Common Mistakes:

• Confusing cache_classes false with caching data
• Thinking eager_load false means eager loading is on
• Assuming classes are cached in development

4. You added this line to config/environments/production.rb:

config.consider_all_requests_local = true

But you still don't see detailed error pages in production. What is the likely problem?

medium

A. Rails does not support detailed errors in production at all

B. The line should be in development.rb, not production.rb

C. You need to restart the server for changes to take effect

D. The setting is overridden by another config file or environment variable

Solution

1. Step 1: Understand consider_all_requests_local

   This setting controls if Rails shows detailed error pages. True means show detailed errors.

2. Step 2: Check why it might not work in production

   Often other configs or environment variables override this setting, preventing detailed errors.

3. Final Answer:

   The setting is overridden by another config file or environment variable -> Option D

4. Quick Check:

   Overridden config blocks detailed errors [OK]

Hint: Check for overrides or env variables blocking changes [OK]

Common Mistakes:

• Assuming detailed errors never show in production
• Not restarting server after config changes
• Putting setting in wrong environment file

5. You want to disable asset debugging only in the test environment without affecting development or production. Which change correctly achieves this in Rails?

medium

A. Add config.assets.debug = false inside config/environments/test.rb

B. Add config.assets.debug = false inside config/environments/production.rb

C. Add config.assets.debug = false inside config/application.rb

D. Add config.assets.debug = false inside config/environments/development.rb

Solution

1. Step 1: Identify environment-specific config location

   To change behavior only in test, put config in config/environments/test.rb.

2. Step 2: Set assets.debug to false in test environment

   Adding config.assets.debug = false in test.rb disables asset debugging only for tests.

3. Final Answer:

   Add config.assets.debug = false inside config/environments/test.rb -> Option A

4. Quick Check:

   Environment-specific config goes in matching environment file [OK]

Hint: Put config in matching environment file to isolate changes [OK]

Common Mistakes:

• Changing config in wrong environment file
• Changing config in application.rb affects all environments
• Forgetting to restart server after changes