Rails 3: rendering views outside a controller

2013-06-24 programming ruby ruby-on-rails

I discovered recently that Ruby on Rails 3’s action views really don’t like it when you try to render them outside a controller. This was a problem, as I wanted to render a view in a Resque background task for caching.

You have to jump through a few hoops to make it work. The trick is to create a subclass of ActionView::Base and mix in a few things it’s missing:

module Renderer

  # Renders a view.
  def self.render options = {}

    # Pass a hash of local variables as :assigns.
    assigns = options.delete(:assigns) || {}

    # Create a view.
    view = view_class.new(
      ActionController::Base.view_paths, assigns
    )

    # Mix in other helpers you need.
    view.extend ApplicationHelper
    view.extend CustomHelper

    # Render.
    view.render options
  end

  # Creates a subclass of ActionView::Base with route
  # helpers mixed in.
  def self.view_class
    @view_class ||= Class.new ActionView::Base do
      include Rails.application.routes.url_helpers
    end
  end
end

You can then use it from wherever:

Renderer.render(
  template: 'users/show',
  assigns: { user: @logged_user }
)

That’s it. Not quite clean but at least it’s short.

Meta