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60 lines
1.5 KiB
Python
60 lines
1.5 KiB
Python
"""Concept example of `Dependency Injector`."""
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import sqlite3
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import dependency_injector as di
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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(di.AbstractCatalog):
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"""Catalog of providers."""
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database = di.Singleton(sqlite3.Connection,
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database=':memory:')
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""":type: (di.Provider) -> sqlite3.Connection"""
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object_a_factory = di.Factory(ObjectA,
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db=database)
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""":type: (di.Provider) -> ObjectA"""
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object_b_factory = di.Factory(ObjectB,
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a=object_a_factory,
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db=database)
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""":type: (di.Provider) -> ObjectB"""
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# Catalog static provides.
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a1, a2 = Catalog.object_a_factory(), Catalog.object_a_factory()
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b1, b2 = Catalog.object_b_factory(), Catalog.object_b_factory()
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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 is Catalog.database()
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# Example of inline injections.
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@di.inject(a=Catalog.object_a_factory)
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@di.inject(b=Catalog.object_b_factory)
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@di.inject(database=Catalog.database)
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def example(a, b, database):
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"""Example callback."""
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assert a.db is b.db is database is Catalog.database()
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example()
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