202 lines
5.0 KiB
ReStructuredText
202 lines
5.0 KiB
ReStructuredText
Advanced usage
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==============
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Below you can find some variants of advanced usage of **Objects**.
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@inject decorator
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-----------------
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``@inject`` decorator could be used for patching any callable with injection.
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Any Python object will be injected *as is*, except **Objects** providers,
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that will be called to provide injectable value.
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.. code-block:: python
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"""`@inject` decorator example."""
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from objects.providers import NewInstance
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from objects.injections import KwArg
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from objects.injections import inject
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new_object = NewInstance(object)
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@inject(KwArg('object_a', new_object))
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@inject(KwArg('some_setting', 1334))
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def example_callback(object_a, some_setting):
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"""This function has dependencies on object a and b.
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Dependencies are injected using `@inject` decorator.
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"""
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assert isinstance(object_a, object)
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assert some_setting == 1334
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example_callback()
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example_callback()
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Overriding providers
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--------------------
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Any provider can be overridden by another provider.
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Example:
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.. code-block:: python
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"""Provider overriding example."""
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import sqlite3
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from objects.providers import Singleton
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from objects.providers import NewInstance
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from objects.injections import KwArg
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from objects.injections import Attribute
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class ObjectA(object):
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"""ObjectA has dependency on database."""
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def __init__(self, database):
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"""Initializer.
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Database dependency need to be injected via init arg."""
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self.database = database
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def get_one(self):
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"""Select one from database and return it."""
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return self.database.execute('SELECT 1')
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class ObjectAMock(ObjectA):
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"""Mock of ObjectA.
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Has no dependency on database.
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"""
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def __init__(self):
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"""Initializer."""
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def get_one(self):
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"""Select one from database and return it.
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Mock makes no database queries and always returns two instead of one.
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"""
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return 2
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# Database and `ObjectA` providers.
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database = Singleton(sqlite3.Connection,
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KwArg('database', ':memory:'),
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KwArg('timeout', 30),
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KwArg('detect_types', True),
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KwArg('isolation_level', 'EXCLUSIVE'),
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Attribute('row_factory', sqlite3.Row))
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object_a = NewInstance(ObjectA,
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KwArg('database', database))
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# Overriding `ObjectA` provider with `ObjectAMock` provider.
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object_a.override(NewInstance(ObjectAMock))
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# Creating several `ObjectA` instances.
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object_a_1 = object_a()
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object_a_2 = object_a()
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# Making some asserts.
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assert object_a_1 is not object_a_2
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assert object_a_1.get_one() == object_a_2.get_one() == 2
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Overriding catalogs
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-------------------
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Any catalog can be overridden by another catalog.
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Example:
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.. code-block:: python
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"""Catalog overriding example."""
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import sqlite3
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from objects.catalog import AbstractCatalog
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from objects.catalog import override
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from objects.providers import Singleton
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from objects.providers import NewInstance
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from objects.injections import KwArg
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from objects.injections import Attribute
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class ObjectA(object):
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"""ObjectA has dependency on database."""
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def __init__(self, database):
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"""Initializer.
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Database dependency need to be injected via init arg."""
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self.database = database
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def get_one(self):
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"""Select one from database and return it."""
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return self.database.execute('SELECT 1')
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class ObjectAMock(ObjectA):
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"""Mock of ObjectA.
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Has no dependency on database.
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"""
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def __init__(self):
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"""Initializer."""
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def get_one(self):
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"""Select one from database and return it.
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Mock makes no database queries and always returns two instead of one.
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"""
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return 2
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class Catalog(AbstractCatalog):
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"""Catalog of objects providers."""
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database = Singleton(sqlite3.Connection,
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KwArg('database', ':memory:'),
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KwArg('timeout', 30),
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KwArg('detect_types', True),
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KwArg('isolation_level', 'EXCLUSIVE'),
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Attribute('row_factory', sqlite3.Row))
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object_a = NewInstance(ObjectA,
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KwArg('database', database))
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@override(Catalog)
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class SandboxCatalog(Catalog):
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"""Sandbox objects catalog with some mocks that overrides Catalog."""
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object_a = NewInstance(ObjectAMock)
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# Creating several `ObjectA` instances.
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object_a_1 = Catalog.object_a()
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object_a_2 = Catalog.object_a()
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# Making some asserts.
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assert object_a_1 is not object_a_2
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assert object_a_1.get_one() == object_a_2.get_one() == 2
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