class DependencyTracker

Action View Dependency Tracker

When the digestor builds a template’s dependency tree (to compute the cache keys used by cache blocks and stale? checks), it asks the dependency tracker which other templates a given template renders.

Dependencies are tracked per template handler, because every template language spells render differently. Action View ships ERBTracker for ERB; handlers for other template languages register their own with ::register_tracker, typically from an +ActiveSupport.on_load(:action_view)+ block so it runs once Action View is available:

ActiveSupport.on_load(:action_view) do
  ActionView::Template.register_template_handler :mtl, MyTemplateLanguage::Handler
  ActionView::DependencyTracker.register_tracker :mtl, MyTemplateLanguage::DependencyTracker
end

Languages whose render calls look like Ruby’s can register ERBTracker instead of writing their own tracker.