Inject Dependencies

inject-dependencies

Use this skill when injecting dependencies into Hanami 2.x components.

Core principle: Dependencies are injected, not looked up. Never access the container directly — always use include Deps[].

Quick Reference

Core Rules

1. Always use include Deps[] to inject dependencies:

   # app/actions/users/index.rb
   # frozen_string_literal: true
   
   module MyApp
     module Actions
       module Users
         class Index < MyApp::Action
            include Deps["repos.user_repo"]
   
            def handle(request, response)
              # `view` is resolved by Hanami from the Action class name convention
              response.render(view, users: user_repo.all)
            end
         end
       end
     end
   end
   

2. The container key is derived from the file path:

   app/repos/user_repo.rb     → "repos.user_repo"
   app/views/users/index.rb   → "views.users.index"
   app/relations/users.rb     → "relations.users"
   

   Rule: app/{dir}/{name}.rb maps to container key "{dir}.{name}".

3. Certain directories are excluded from auto-registration because ROM manages them directly:

   • relations/
   • structs/
   • entities/

   These are handled by ROM and should not be auto-registered by dry-system.

4. Add custom exclusions in the slice configuration:

   # config/app.rb
   # frozen_string_literal: true
   
   module MyApp
     class App < Hanami::App
       config.no_auto_register_paths = ["app/serializers"]
     end
   end
   

5. Override dependencies in tests by passing them to .new:

   stub_repo = double("user_repo", all: [])
   action = MyApp::Actions::Users::Index.new(user_repo: stub_repo)
   

6. Never access the container directly:

   # BAD
   repo = Hanami.app["repos.user_repo"]
   
   # GOOD
   include Deps["repos.user_repo"]
   # use user_repo directly
   

Anti-Patterns & Mistakes