Action Pack is a framework for handling and responding to web requests. It provides mechanisms for routing (mapping request URLs to actions), defining controllers that implement actions, and generating responses by rendering views, which are templates of various formats. In short, Action Pack provides the view and controller layers in the MVC paradigm. And if you read the page on Active Record, you know that Active Record provides the model part.
It consists of several modules:
- Action Dispatch, which parses information about the web request, handles routing as defined by the user, and does advanced processing related to HTTP such as MIME-type negotiation, decoding parameters in POST, PATCH, or PUT bodies, handling HTTP caching logic, cookies and sessions.
- Action Controller, which provides a base controller class that can be subclassed to implement filters and actions to handle requests. The result of an action is typically content generated from views.
- Action View, which handles view template lookup and rendering, and provides view helpers that assist when building HTML forms, Atom feeds and more. Template formats that Action View handles are ERB (embedded Ruby, typically used to inline short Ruby snippets inside HTML), and XML Builder.
With the Ruby on Rails framework, users only directly interface with the Action Controller module. Necessary Action Dispatch functionality is activated by default and Action View rendering is implicitly triggered by Action Controller. However, these modules are designed to function on their own and can be used outside of Rails.