Implementing Dependency Injection

Inject dependencies through the constructor using Hanami's auto_inject — never call the container directly.

Quick Reference

• Pattern: include Deps["provider_key"] in actions, operations, or repositories.
• Testing: Pass test doubles through the constructor in specs.
• Providers: Dependencies must be registered by a provider first.
• Rule: Never call Hanami.app["key"] outside of providers.

HARD-GATE

DO NOT call the container directly (`Hanami.app["key"]`) outside of providers.
DO NOT use global state or class-level constants for dependencies.
DO inject dependencies through the constructor — use `include Deps[...]`.

Core Process

1. Verify the provider — ensure the dependency is registered in a provider under a descriptive key.
2. Add injection in the consuming class:

   module Api
     module Actions
       module Users
         class Create < Api::Action
           include Deps["operations.users.create_user"]
   
           def handle(req, res)
             result = create_user.call(req.params.to_h)
             # ...
           end
         end
       end
     end
   end

3. For operations, inject repositories and other operations:

   module Users
     class CreateUser < Dry::Operation
       include Deps["repositories.user_repo", "operations.notifications.send_welcome"]
   
       def call(input)
         # ...
       end
     end
   end

4. For repositories, inject ROM if needed:

   module Api
     module Repositories
       class UserRepo < ROM::Repository[:users]
         # Auto-injected if using auto_registration
       end
     end
   end

5. Test with stubs — inject test doubles through the constructor:

   RSpec.describe Api::Actions::Users::Create do
     let(:create_user) { instance_double(Users::CreateUser, call: Dry::Monads::Success(user)) }
     let(:action) { described_class.new(create_user:) }
   end

   See TESTING_DI.md for detailed testing patterns.

Extended Resources (Progressive Disclosure)

Load these files only when needed:

• TESTING_DI.md — Testing patterns for injected dependencies: stubs, mocks, contract verification.

Output Style

1. Class with DI — the complete class with include Deps[...].
2. Provider key — the exact key used for registration.
3. Test example — how to pass a test double through the constructor.
4. English only unless user requests otherwise.

Integration