Add factory patterns

Author: rmk135

examples/miniapps/factory_patterns/chained_factories.py

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+"""`Chained Factories` pattern."""
+
+from dependency_injector import providers
+
+from data import (
+    id_generator,
+    session,
+    SqlAlchemyDatabaseService,
+    TokensService,
+    Token,
+    UsersService,
+    User,
+)
+
+
+# "Chained Factories" pattern
+
+database = providers.Factory(SqlAlchemyDatabaseService, session=session)
+
+tokens = providers.Factory(
+    TokensService,
+    id_generator=id_generator,
+    database=providers.Factory(database, base_class=Token),
+)
+
+users = providers.Factory(
+    UsersService,
+    id_generator=id_generator,
+    database=providers.Factory(database, base_class=User),
+)
+
+tokens_service = tokens()
+assert tokens_service.database.base_class is Token
+
+users_service = users()
+assert users_service.database.base_class is User
+
+# Explanation & some more examples
+
+# 1. Keyword arguments of upper level factory are added to lower level factory
+chained_dict_factory = providers.Factory(
+    providers.Factory(dict, arg1=1),
+    arg2=2,
+)
+print(chained_dict_factory())  # prints: {'arg1': 1, 'arg2': 2}
+
+# 2. Keyword arguments of upper level factory have priority
+chained_dict_factory = providers.Factory(
+    providers.Factory(dict, arg1=1),
+    arg1=2,
+)
+print(chained_dict_factory())  # prints: {'arg1': 2}
+
+# 3. Keyword arguments provided from context have most priority
+chained_dict_factory = providers.Factory(
+    providers.Factory(dict, arg1=1),
+    arg1=2,
+)
+print(chained_dict_factory(arg1=3))  # prints: {'arg1': 3}

examples/miniapps/factory_patterns/data.py

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+"""Sample data classes."""
+
+
+class SqlAlchemyDatabaseService:
+    """Database service of an entity."""
+
+    def __init__(self, session, base_class):
+        """Initialize object."""
+        self.session = session
+        self.base_class = base_class
+
+
+class TokensService:
+    """Tokens service."""
+
+    def __init__(self, id_generator, database):
+        """Initialize object."""
+        self.id_generator = id_generator
+        self.database = database
+
+
+class Token:
+    """Token entity."""
+
+
+class UsersService:
+    """Users service."""
+
+    def __init__(self, id_generator, database):
+        """Initialize object."""
+        self.id_generator = id_generator
+        self.database = database
+
+
+class User:
+    """User entity."""
+
+
+# Sample objects
+session = object()
+id_generator = object()

examples/miniapps/factory_patterns/factory_of_factories.py

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+"""`Factory of Factories` pattern."""
+
+from dependency_injector import providers
+
+from data import (
+    id_generator,
+    session,
+    SqlAlchemyDatabaseService,
+    TokensService,
+    Token,
+    UsersService,
+    User,
+)
+
+
+# "Factory of Factories" pattern
+
+database_factory = providers.Factory(
+    providers.Factory,
+    SqlAlchemyDatabaseService,
+    session=session,
+)
+
+tokens = providers.Factory(
+    TokensService,
+    id_generator=id_generator,
+    database=database_factory(base_class=Token),
+)
+
+users = providers.Factory(
+    UsersService,
+    id_generator=id_generator,
+    database=database_factory(base_class=User),
+)
+
+tokens_service = tokens()
+assert tokens_service.database.base_class is Token
+
+users_service = users()
+assert users_service.database.base_class is User
+
+# Explanation & some more examples
+
+# 1. Keyword arguments of upper level factory are added to lower level factory
+factory_of_dict_factories = providers.Factory(
+    providers.Factory,
+    dict,
+    arg1=1,
+)
+dict_factory = factory_of_dict_factories(arg2=2)
+print(dict_factory())  # prints: {'arg1': 1, 'arg2': 2}
+
+# 2. Keyword arguments of upper level factory have priority
+factory_of_dict_factories = providers.Factory(
+    providers.Factory,
+    dict,
+    arg1=1,
+)
+dict_factory = factory_of_dict_factories(arg1=2)
+print(dict_factory())  # prints: {'arg1': 2}
+
+# 3. Keyword arguments provided from context have most priority
+factory_of_dict_factories = providers.Factory(
+    providers.Factory,
+    dict,
+    arg1=1,
+)
+dict_factory = factory_of_dict_factories(arg1=2)
+print(dict_factory(arg1=3))  # prints: {'arg1': 3}