ACTIONVIEW

ActionView is a component of the Ruby on Rails web framework that handles the presentation layer by rendering templates, partials, and layouts. It provides helpers to generate HTML and other content and integrates with the controller to present data to users.

Templates may be written in various template languages, such as ERB, Haml, or Slim, and are stored in view paths under an application. Rails resolves templates based on the controller, action, and format and renders them in a view context that exposes instance variables and locals.

ActionView includes a rich set of helpers (ActionView::Helpers) for tasks such as generating forms, links, tags, and escaping HTML. It supports layouts, partials for reuse, and a system of render calls that can pass locals to partials. The template system is pluggable via template handlers.

Data flow: a controller action prepares data, calls render, and ActionView combines the selected template with layout, applies helpers and I18n translations, and escapes content as appropriate before sending the response.

Caching and performance: ActionView supports fragment caching of template fragments to avoid recomputation, and view caching can be controlled with standard Rails caching mechanisms. The rendering pipeline is designed to be extensible via custom helpers and components.

ActionView is designed to work closely with ActionController but is usable in standalone contexts, and remains a central part of Rails’ separation of concerns between business logic and presentation.