Adding delegate option for injections

examples/singleton_and_factory.py

@@ -0,0 +1,69 @@
+"""Providers delegation example."""
+
+from objects.providers import Factory
+from objects.providers import Singleton
+
+from objects.injections import KwArg
+
+
+class User(object):
+
+    """Example class User."""
+
+    def __init__(self, id, name):
+        """Initializer.
+
+        :param id: int
+        :param name: str
+        :return:
+        """
+        self.id = id
+        self.name = name
+
+
+class UserService(object):
+
+    """Example class UserService.
+
+    UserService has dependency on users factory.
+    """
+
+    def __init__(self, users_factory):
+        """Initializer.
+
+        :param users_factory: objects.providers.Factory
+        :return:
+        """
+        self.users_factory = users_factory
+
+    def get_by_id(self, id):
+        """Return user info by user id."""
+        return self.users_factory(id=id, name=self._get_name_from_db(id))
+
+    def _get_name_from_db(self, id):
+        """Return user's name from database by his id.
+
+        Main purpose of this method is just to show the fact of retrieving
+        some user's data from database, so, actually, it simulates work
+        with database just by merging constant string with provided user's id.
+        """
+        return ''.join(('user', str(id)))
+
+
+# Users factory and UserService provider:
+users_service = Singleton(UserService,
+                          KwArg('users_factory',
+                                Factory(User),
+                                delegate=True))
+
+
+# Creating several User objects:
+user1 = users_service().get_by_id(1)
+user2 = users_service().get_by_id(2)
+
+# Making some asserts:
+assert user1.id == 1
+assert user1.name == 'user1'
+
+assert user2.id == 2
+assert user2.name == 'user2'

objects/injections.py

@@ -8,17 +8,18 @@ class Injection(object):
     """Base injection class."""
 
     __IS_OBJECTS_INJECTION__ = True
-    __slots__ = ('name', 'injectable')
+    __slots__ = ('name', 'injectable', 'delegate')
 
-    def __init__(self, name, injectable):
+    def __init__(self, name, injectable, delegate=False):
         """Initializer."""
         self.name = name
         self.injectable = injectable
+        self.delegate = delegate
 
     @property
     def value(self):
         """Return injectable value."""
-        if is_provider(self.injectable):
+        if is_provider(self.injectable) and not self.delegate:
             return self.injectable()
         return self.injectable