DependencyInjector._get_argument() - Code Metrics - Inspection of "Clean unit tests" - Darkheir/pyjection - Measure and Improve Code Quality continuously with Scrutinizer

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by Raphaël

created 2016-05-16 20:38 UTC

DependencyInjector._get_argument() B

↳ Parent: DependencyInjector

Complexity

Conditions

Size

Total Lines

Duplication

Lines	0
Ratio	0 %

Code Coverage

Tests	6
CRAP Score	9.3798

Importance

Changes	2
Bugs	0	Features	0

Metric	Value
c	2
b	0
f	0
dl	0
loc	26
ccs	6
cts	11
cp	0.5455
rs	7.5384
cc	6
crap	9.3798

from inspect import signature
from inspect import Parameter
from collections import OrderedDict
from pyjection.service import Service
from pyjection.reference import Reference


class DependencyInjector(object):

    def __init__(self):
        self._services = dict()
        self._singletons = dict()

    def register(self, identifier, service_subject):
        """
        Register a new service in the dependency injector

        This service can be :
            * A class that will be instantiated when called
            * An already instantiated instance that will be returned

        :param identifier: The identifier used to later retrieve a service instance
        :type identifier: string
        :param service_subject: The class or instance
        :type service_subject: mixed

        :return: Return the newly created service entry
        :rtype: Service
        """
        service = Service(service_subject)
        self._services[identifier] = service
        return service

    def register_singleton(self, identifier, service_subject):
        """
        Register a new singleton service in in the dependency injector

        This service can be :
            * A class that will be instantiated when called
            * An already instantiated instance that will be returned

        :param identifier: The identifier used to later retrieve a service singleton
        :type identifier: string
        :param service_subject: The class or instance
        :type service_subject: mixed

        :return: Return the newly created dependency entry
        :rtype: Service
        """
        service = Service(service_subject)
        service.is_singleton = True
        self._services[identifier] = service
        return service

    def get(self, identifier):
        """
        Instantiate and retrieve the service matching this identifier

        If the service has been self has a singleton the same service object
        will be return each time this service is asked

        :param identifier: The identifier used to later retrieve a class singleton
        :type identifier: string
        :return: The instantiated object
        :rtype: mixed
        """
        if self.has_service(identifier) is False:
            raise Exception("No service has been declared with this ID")

        service = self._services[identifier]
        instance = self._get_singleton(identifier, service)
        if instance is not None:
            return instance

        instance = self._get_instance(service)
        self._set_singleton(identifier, instance, service)

        return instance

    def has_service(self, identifier):
        """
        Check if the service matching the given identifier
        has already been declared

        :param identifier: Name of the service
        :type identifier: string
        :return: Whether or not the service exists
        :rtype: boolean
        """
        if identifier in self._services:
            return True
        return False

    def _get_singleton(self, identifier, service):
        """
        Return the singleton if it has been setted and
        the service represents a singleton

        :param identifier: the singleton identifier
        :param service: The service we need the singleton for
        :type identifier: string
        :type service: Service

        :return: The singleton instance or None
        :rtype: mixed
        """
        if service.is_singleton is True and identifier in self._singletons:
            return self._singletons[identifier]
        return None

    def _set_singleton(self, identifier, instance, service):
        """
        Set the instance as a singleton in the dict
        if the service represents a singleton

        :param identifier: the singleton identifier
        :param service: The service we want to set a singleton for
        :param instance: The singleton instance
        :type identifier: string
        :type service: Service
        :type instance: mixed
        """
        if service.is_singleton is True:
            self._singletons[identifier] = instance

    def _get_instance(self, service):
        """
        Return the instantiated object for the given service

        :param service: The service we need an instance for
        :type service: Service
        :return: The instantiated object
        """
        if service.type == 'instance':
            return service.subject
        arguments = self._generate_arguments_dict(service)
        return service.subject(**arguments)

    def _generate_arguments_dict(self, service):
        """
        Generate a dict containing all the parameters values
        required to Instantiate the service.

        An exception is raised if a mandatory argument cannot be
        retrieved.

        :param service: The service that needs to be instantiated
        :type service: Service
        :return: The parameters values to use to instantiate the service
        :rtype: dict
        """
        arguments = dict()

        # We can't use signature on object __init__
        if self._is_object_init(service.subject) is True:
            return arguments

        sig = signature(service.subject.__init__)
        method_parameters = OrderedDict(sig.parameters)

        # Pop the first param since it's the self class instance
        method_parameters.popitem(False)

        for method_parameter in method_parameters.values():
            argument = self._get_argument(service, method_parameter)
            if argument is not None:
                arguments[method_parameter.name] = argument

        return arguments

    def _is_object_init(self, subject):
        """
        Check if the __init__ method for the object comes from
        the default object or has been overridden

        :param subject: The subject we want to check the __init__ for
        :type subject: mixed

        :return: Whether the __init__ method is the default on or not
        :rtype: boolean
        """
        if '__objclass__' in dir(subject.__init__) and subject.__init__.__objclass__ == object:
            return True
        return False

    def _get_argument(self, service, method_parameter):
        """
        Retrieve the argument value for the given service

        :param service: The service we need an argument for
        :param method_parameter: The parameter we need the value for
        :type service: Service
        :type method_parameter: Parameter
        :return: The argument value
        :rtype: mixed
        """
        if method_parameter.name in service.arguments:
            value = service.arguments[method_parameter.name]
            # The value references an other dependency service
            if isinstance(value, Reference):
                return self.get(value.name)
            return value

        # If the parameter is *args or **kwargs then we don't raise any exception
        if method_parameter.kind == Parameter.VAR_POSITIONAL or \
                method_parameter.kind == Parameter.VAR_KEYWORD:
            return None
        # If the parameter has a default value then we don't raise any exception
        if method_parameter.default is not Parameter.empty:
            return None
        raise Exception("A required argument is not set (%s)" % method_parameter.name)


1	1	from inspect import signature
2	1	from inspect import Parameter
3	1	from collections import OrderedDict
4	1	from pyjection.service import Service
5	1	from pyjection.reference import Reference
6
7
8	1	class DependencyInjector(object):
9
10	1	def __init__(self):
11	1	self._services = dict()
12	1	self._singletons = dict()
13
14	1	def register(self, identifier, service_subject):
15		"""
16		Register a new service in the dependency injector
17
18		This service can be :
19		* A class that will be instantiated when called
20		* An already instantiated instance that will be returned
21
22		:param identifier: The identifier used to later retrieve a service instance
23		:type identifier: string
24		:param service_subject: The class or instance
25		:type service_subject: mixed
26
27		:return: Return the newly created service entry
28		:rtype: Service
29		"""
30	1	service = Service(service_subject)
31	1	self._services[identifier] = service
32	1	return service
33
34	1	def register_singleton(self, identifier, service_subject):
35		"""
36		Register a new singleton service in in the dependency injector
37
38		This service can be :
39		* A class that will be instantiated when called
40		* An already instantiated instance that will be returned
41
42		:param identifier: The identifier used to later retrieve a service singleton
43		:type identifier: string
44		:param service_subject: The class or instance
45		:type service_subject: mixed
46
47		:return: Return the newly created dependency entry
48		:rtype: Service
49		"""
50	1	service = Service(service_subject)
51	1	service.is_singleton = True
52	1	self._services[identifier] = service
53	1	return service
54
55	1	def get(self, identifier):
56		"""
57		Instantiate and retrieve the service matching this identifier
58
59		If the service has been self has a singleton the same service object
60		will be return each time this service is asked
61
62		:param identifier: The identifier used to later retrieve a class singleton
63		:type identifier: string
64		:return: The instantiated object
65		:rtype: mixed
66		"""
67	1	if self.has_service(identifier) is False:
68	1	raise Exception("No service has been declared with this ID")
69
70	1	service = self._services[identifier]
71	1	instance = self._get_singleton(identifier, service)
72	1	if instance is not None:
73	1	return instance
74
75	1	instance = self._get_instance(service)
76	1	self._set_singleton(identifier, instance, service)
77
78	1	return instance
79
80	1	def has_service(self, identifier):
81		"""
82		Check if the service matching the given identifier
83		has already been declared
84
85		:param identifier: Name of the service
86		:type identifier: string
87		:return: Whether or not the service exists
88		:rtype: boolean
89		"""
90	1	if identifier in self._services:
91	1	return True
92	1	return False
93
94	1	def _get_singleton(self, identifier, service):
95		"""
96		Return the singleton if it has been setted and
97		the service represents a singleton
98
99		:param identifier: the singleton identifier
100		:param service: The service we need the singleton for
101		:type identifier: string
102		:type service: Service
103
104		:return: The singleton instance or None
105		:rtype: mixed
106		"""
107	1	if service.is_singleton is True and identifier in self._singletons:
108	1	return self._singletons[identifier]
109	1	return None
110
111	1	def _set_singleton(self, identifier, instance, service):
112		"""
113		Set the instance as a singleton in the dict
114		if the service represents a singleton
115
116		:param identifier: the singleton identifier
117		:param service: The service we want to set a singleton for
118		:param instance: The singleton instance
119		:type identifier: string
120		:type service: Service
121		:type instance: mixed
122		"""
123	1	if service.is_singleton is True:
124	1	self._singletons[identifier] = instance
125
126	1	def _get_instance(self, service):
127		"""
128		Return the instantiated object for the given service
129
130		:param service: The service we need an instance for
131		:type service: Service
132		:return: The instantiated object
133		"""
134	1	if service.type == 'instance':
135	1	return service.subject
136	1	arguments = self._generate_arguments_dict(service)
137	1	return service.subject(**arguments)
138
139	1	def _generate_arguments_dict(self, service):
140		"""
141		Generate a dict containing all the parameters values
142		required to Instantiate the service.
143
144		An exception is raised if a mandatory argument cannot be
145		retrieved.
146
147		:param service: The service that needs to be instantiated
148		:type service: Service
149		:return: The parameters values to use to instantiate the service
150		:rtype: dict
151		"""
152	1	arguments = dict()
153
154		# We can't use signature on object __init__
155	1	if self._is_object_init(service.subject) is True:
156		return arguments
157
158	1	sig = signature(service.subject.__init__)
159	1	method_parameters = OrderedDict(sig.parameters)
160
161		# Pop the first param since it's the self class instance
162	1	method_parameters.popitem(False)
163
164	1	for method_parameter in method_parameters.values():
165	1	argument = self._get_argument(service, method_parameter)
166	1	if argument is not None:
167		arguments[method_parameter.name] = argument
168
169	1	return arguments
170
171	1	def _is_object_init(self, subject):
172		"""
173		Check if the __init__ method for the object comes from
174		the default object or has been overridden
175
176		:param subject: The subject we want to check the __init__ for
177		:type subject: mixed
178
179		:return: Whether the __init__ method is the default on or not
180		:rtype: boolean
181		"""
182	1	if '__objclass__' in dir(subject.__init__) and subject.__init__.__objclass__ == object:
183		return True
184	1	return False
185
186	1	def _get_argument(self, service, method_parameter):
187		"""
188		Retrieve the argument value for the given service
189
190		:param service: The service we need an argument for
191		:param method_parameter: The parameter we need the value for
192		:type service: Service
193		:type method_parameter: Parameter
194		:return: The argument value
195		:rtype: mixed
196		"""
197	1	if method_parameter.name in service.arguments:
198		value = service.arguments[method_parameter.name]
199		# The value references an other dependency service
200		if isinstance(value, Reference):
201		return self.get(value.name)
202		return value
203
204		# If the parameter is args or *kwargs then we don't raise any exception
205	1	if method_parameter.kind == Parameter.VAR_POSITIONAL or \
206		method_parameter.kind == Parameter.VAR_KEYWORD:
207	1	return None
208		# If the parameter has a default value then we don't raise any exception
209	1	if method_parameter.default is not Parameter.empty:
210	1	return None
211		raise Exception("A required argument is not set (%s)" % method_parameter.name)
212

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DependencyInjector._get_argument() B

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