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Separate JavaScript Importmaps For Rails Engines

November 12, 2024

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Your Teacher

Chris Oliver

Hi, I'm Chris. I'm the creator of GoRails, Hatchbox.io and Jumpstart. I spend my time creating tutorials and tools to help Ruby on Rails developers build apps better and faster.

About This Episode

Rails engines often need a way of providing JavaScript for their views. We can do this using Importmaps regardless of what the application is using for assets.

Notes

Create a new Importmap::Map:

module MyEngine
  mattr_accessor :importmap, default: Importmap::Map.new
end

Pin imports

module MyEngine
  class Engine < ::Rails::Engine
    initializer "my_engine.importmap" do
      MyEngine.importmap.draw root.join("config/importmap.rb")
      MyEngine.importmap.cache_sweeper watches: root.join("app/javascript")

      ActiveSupport.on_load(:action_controller_base) do
        before_action { MyEngine.importmap.cache_sweeper.execute_if_updated }
      end
    end
  end
end

Render it in the view:

<%= javascript_importmap_tags "application", importmap: MyEngine.importmap %>

View this lesson's source code