Manifest Files and Directives

In the assets initalizer (config/initializers/assets.rb) are a few files explicitly defined to be precompiled.

# Precompile additional assets.
# application.coffee, application.scss, and all non-JS/CSS in app/assets folder are already added.
# Rails.application.config.assets.precompile += %w( search.js )

In this example the application.coffee and application.scss are so called ‘Manifest Files’. This files should be used to include other JavaScript or CSS assets. The following command are available:

• require <path>: The require directive functions similar to Ruby’s own require. It provides a way to declare a dependency on a file in your path and ensures it’s only loaded once before the source file.
• require_directory <path>: requires all the files inside a single directory. It’s similar to path/* since it does not follow nested directories.
• require_tree <path>: requires all the nested files in a directory. Its glob equivalent is path/**/*.
• require_self: causes the body of the current file to be inserted before any subsequent require directives. Useful in CSS files, where it’s common for the index file to contain global styles that need to be defined before other dependencies are loaded.
• stub <path>: remove a file from being included
• depend_on <path>: Allows you to state a dependency on a file without including it. This is used for caching purposes. Any changes made to the dependency file will invalidate the cache of the source file.

An application.scss file could look like:

/*
 *= require bootstrap
 *= require_directory .
 *= require_self
 */

Another example is the application.coffee file. Here with including jquery and Turbolinks:

#= require jquery2
#= require jquery_ujs
#= require turbolinks
#= require_tree .

If you don’t use CoffeeScript, but plain JavaScript, the syntax would be:

//= require jquery2
//= require jquery_ujs
//= require turbolinks
//= require_tree .