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https://github.com/ets-labs/python-dependency-injector.git
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107 lines
2.6 KiB
Python
107 lines
2.6 KiB
Python
"""Concept example of objects catalogs."""
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from objects.catalog import AbstractCatalog
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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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from objects.errors import Error
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import sqlite3
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class ObjectA(object):
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"""Example class ObjectA, that has dependency on database."""
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def __init__(self, db):
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"""Initializer."""
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self.db = db
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class ObjectB(object):
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"""Example class ObjectB, that has dependencies on ObjectA and database."""
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def __init__(self, a, db):
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"""Initializer."""
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self.a = a
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self.db = db
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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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Attribute('row_factory', sqlite3.Row))
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""":type: (objects.Provider) -> sqlite3.Connection"""
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object_a = NewInstance(ObjectA,
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KwArg('db', database))
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""":type: (objects.Provider) -> ObjectA"""
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object_b = NewInstance(ObjectB,
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KwArg('a', object_a),
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KwArg('db', database))
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""":type: (objects.Provider) -> ObjectB"""
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# Dependencies injection into class.
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class Consumer(object):
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"""Example consumer class."""
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dependencies = Catalog(Catalog.object_a,
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Catalog.object_b)
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def example(self):
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"""Example method."""
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a1 = self.dependencies.object_a()
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a2 = self.dependencies.object_a()
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b1 = self.dependencies.object_b()
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b2 = self.dependencies.object_b()
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# Some asserts.
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assert a1 is not a2
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assert b1 is not b2
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assert a1.db is a2.db is b1.db is b2.db
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try:
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self.dependencies.database()
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except Error:
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pass
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else:
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raise Exception('Database is not listed as a dependency')
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Consumer().example()
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# Dependencies injection (The Python Way) into a callback.
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def consumer_callback(dependencies=Catalog(Catalog.object_a,
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Catalog.object_b)):
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"""Example function."""
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a1 = dependencies.object_a()
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a2 = dependencies.object_a()
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b1 = dependencies.object_b()
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b2 = dependencies.object_b()
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# Some asserts.
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assert a1 is not a2
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assert b1 is not b2
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assert a1.db is a2.db is b1.db is b2.db
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try:
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dependencies.database()
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except Error:
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pass
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else:
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raise Exception('Database is not listed as a dependency')
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