Add commands and handlers example

docs/main/changelog.rst

@@ -11,6 +11,8 @@ Develop
 -------
 - Add support of non-string keys for ``Dict`` provider.
 - Add simple ``FastAPI`` example.
+- Add ``Commands  and Handlers`` example from
+  issue `#327 <https://github.com/ets-labs/python-dependency-injector/issues/327>`_.
 - Add extra typing test for provided instance of ``DependenciesContainer`` provider.
 
 4.4.1

examples/miniapps/commands-and-handlers/README.rst

@@ -0,0 +1,14 @@
+Commands and Handlers Example
+=============================
+
+This mixed example from issue `#327 <https://github.com/ets-labs/python-dependency-injector/issues/327>`_.
+It demonstrates ``Dict`` provider with non-string keys and ``.provided`` attribute.
+
+Run
+---
+
+To run the application do:
+
+.. code-block:: bash
+
+    python -m application

examples/miniapps/commands-and-handlers/application/__init__.py

@@ -0,0 +1 @@
+"""Top-level package."""

examples/miniapps/commands-and-handlers/application/__main__.py

@@ -0,0 +1,12 @@
+"""Main module."""
+
+from .containers import Container
+from .commands import SaveRating, DoSomethingElse
+
+
+if __name__ == '__main__':
+    container = Container()
+    message_bus = container.message_bus()
+
+    message_bus.handle(SaveRating)
+    message_bus.handle(DoSomethingElse)

examples/miniapps/commands-and-handlers/application/commands.py

@@ -0,0 +1,12 @@
+"""Commands module."""
+
+class Command:
+    ...
+
+
+class SaveRating(Command):
+    ...
+
+
+class DoSomethingElse(Command):
+    ...

examples/miniapps/commands-and-handlers/application/containers.py

@@ -0,0 +1,23 @@
+"""Containers module."""
+
+from dependency_injector import containers, providers
+
+from . import repositories, handler, messagebus, commands
+
+
+class Container(containers.DeclarativeContainer):
+
+    rating_repository = providers.Singleton(repositories.RatingRepository)
+
+    command_handler = providers.Singleton(
+        handler.CommandHandler,
+        rating_repo=rating_repository,
+    )
+
+    message_bus = providers.Factory(
+        messagebus.MessageBus,
+        command_handlers=providers.Dict({
+            commands.SaveRating: command_handler.provided.save_rating,
+            commands.DoSomethingElse: command_handler.provided.something_else,
+        }),
+    )

examples/miniapps/commands-and-handlers/application/handler.py

@@ -0,0 +1,14 @@
+"""Handlers module."""
+
+from .repositories import RatingRepository
+
+
+class CommandHandler:
+    def __init__(self, rating_repo: RatingRepository):
+        self.rating_repo = rating_repo
+
+    def save_rating(self):
+        print('Saving rating')
+
+    def something_else(self):
+        print('Doing something else')

examples/miniapps/commands-and-handlers/application/messagebus.py

@@ -0,0 +1,14 @@
+"""Message bus module."""
+
+from typing import Dict, Callable, Any
+
+from .commands import Command
+
+
+class MessageBus:
+
+    def __init__(self, command_handlers: Dict[str, Callable[..., Any]]):
+        self.command_handlers = command_handlers
+
+    def handle(self, command: Command):
+        self.command_handlers[command]()

examples/miniapps/commands-and-handlers/application/repositories.py

@@ -0,0 +1,5 @@
+"""Repositories module."""
+
+
+class RatingRepository:
+    ...