114 lines
3.0 KiB
Python
114 lines
3.0 KiB
Python
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"""Concept example of `Dependency Injector`."""
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import sqlite3
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from dependency_injector import catalogs
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from dependency_injector import providers
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from dependency_injector import injections
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class UsersService(object):
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"""Users service, 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 AuthService(object):
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"""Auth service, that has dependencies on users service and database."""
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def __init__(self, db, users_service):
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"""Initializer."""
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self.db = db
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self.users_service = users_service
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class Services(catalogs.DeclarativeCatalog):
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"""Catalog of service providers."""
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@providers.Singleton
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def database():
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"""Provide database connection.
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:rtype: providers.Provider -> sqlite3.Connection
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"""
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return sqlite3.connect(':memory:')
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@providers.Factory
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@injections.inject(db=database)
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def users(**kwargs):
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"""Provide users service.
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:rtype: providers.Provider -> UsersService
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"""
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return UsersService(**kwargs)
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@providers.Factory
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@injections.inject(db=database)
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@injections.inject(users_service=users)
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def auth(**kwargs):
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"""Provide users service.
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:rtype: providers.Provider -> AuthService
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"""
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return AuthService(**kwargs)
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# Retrieving catalog providers:
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users_service = Services.users()
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auth_service = Services.auth()
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# Making some asserts:
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assert users_service.db is auth_service.db is Services.database()
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assert isinstance(auth_service.users_service, UsersService)
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assert users_service is not Services.users()
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assert auth_service is not Services.auth()
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# Making some "inline" injections:
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@injections.inject(users_service=Services.users)
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@injections.inject(auth_service=Services.auth)
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@injections.inject(database=Services.database)
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def example(users_service, auth_service, database):
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"""Example callback."""
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assert users_service.db is auth_service.db
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assert auth_service.db is database
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assert database is Services.database()
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# Making a call of decorated callback:
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example()
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# Overriding auth service provider and making some asserts:
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class ExtendedAuthService(AuthService):
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"""Extended version of auth service."""
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def __init__(self, db, users_service, ttl):
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"""Initializer."""
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self.ttl = ttl
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super(ExtendedAuthService, self).__init__(db=db,
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users_service=users_service)
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class OverriddenServices(Services):
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"""Catalog of service providers."""
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@providers.override(Services.auth)
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@providers.Factory
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@injections.inject(db=Services.database)
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@injections.inject(users_service=Services.users)
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@injections.inject(ttl=3600)
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def auth(**kwargs):
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"""Provide users service.
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:rtype: providers.Provider -> AuthService
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"""
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return ExtendedAuthService(**kwargs)
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auth_service = Services.auth()
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assert isinstance(auth_service, ExtendedAuthService)
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