You should be relatively familiar with the Rails file structure having basically built a version of Rails using Sinatra. Below is the standard file structure of a Rails 4.2 app, which is automatically generated when you generate a new rails app with rails new. Look for comments explaining some new directories and files you may not be familiar with.
app_name/
├── app
│ ├── assets # For js and css that you've written
│ │ ├── images
│ │ ├── javascripts
│ │ │ └── application.js # A manifest file for the asset pipeline
│ │ └── stylesheets
│ │ └── application.css # A manifest file for the asset pipeline
│ ├── controllers
│ │ ├── application_controller.rb # From which all controllers inherit from
│ │ └── concerns # For keeping reusable code that applies to all controllers
│ ├── helpers # For view helper modules
│ │ └── application_helper.rb
│ ├── mailers # For code pertaining to sending emails
│ ├── models
│ │ └── concerns # For keeping reusable code that applies to all models
│ └── views
│ └── layouts
│ └── application.html.erb # For HTML that will be on all web pages. <head> tag for example
├── bin # Rails command line tools; we have a few extras with flatiron-rails
│ ├── bundle
│ ├── rails
│ ├── rake
│ ├── setup
│ └── spring
├── config # Configuration code
│ ├── application.rb # Loads rails gems, gems for the specified Rail.env, and configures the application
│ ├── boot.rb # Sets up Bundler and load paths
│ ├── database.yml # Database configuration
│ ├── environment.rb # Runs all initializers
│ ├── environments # Settings for specific environments, production, testing, development, etc.
│ │ ├── development.rb
│ │ ├── production.rb
│ │ └── test.rb
│ ├── initializers # These configuration files load after the framework and gems
│ │ ├── assets.rb
│ │ ├── backtrace_silencers.rb
│ │ ├── cookies_serializer.rb
│ │ ├── filter_parameter_logging.rb
│ │ ├── inflections.rb
│ │ ├── mime_types.rb
│ │ ├── session_store.rb
│ │ └── wrap_parameters.rb
│ ├── locales # For language/international configuration. If you want your app in multiple languages!
│ │ └── en.yml # English localization file
│ ├── routes.rb # Where we build our routes for requests to our app
│ └── secrets.yml # Rails' built in secret key management
├── config.ru # For Rack-based servers to start the application
├── db # database files. Migrations, seed files, etc.
│ └── seeds.rb
├── lib # External libraries go here
│ ├── assets
│ └── tasks
├── log # Error logs live here
├── public # files for the web server that don't change. Static web pages.
│ ├── 404.html
│ ├── 422.html
│ ├── 500.html
│ ├── favicon.ico
│ └── robots.txt
├── spec # all tests
│ ├── feature_helper.rb
│ ├── features
│ ├── rails_helper.rb # As of RSpec 3.x this replaces spec_helper
│ └── spec_helper.rb
├── tmp # Where Rails holds temporary files for immediate processing
│ └── cache
│ └── assets
├── vendor # Where we keep third-party assets (like Bootstrap Themes)
│ └── assets
│ ├── javascripts
│ └── stylesheets
├── Gemfile
├── Gemfile.lock
├── README.rdoc
└── RakefileView The Rails File Structure on Learn.co and start learning to code for free.
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