python-dependency-injector/examples/external_dependency.py

"""
Concept example of objects catalogs.
"""

from objects import AbstractCatalog
from objects.providers import Singleton, NewInstance, ExternalDependency
from objects.injections import InitArg, Attribute

import sqlite3


# Some example classes.
class ObjectA(object):
    def __init__(self, db):
        self.db = db


class ObjectB(object):
    def __init__(self, a, db):
        self.a = a
        self.db = db


# Catalog of objects providers.
class Catalog(AbstractCatalog):
    """
    Objects catalog.
    """

    database = ExternalDependency(instance_of=sqlite3.Connection)
    """ :type: (objects.Provider) -> sqlite3.Connection """

    object_a = NewInstance(ObjectA,
                           InitArg('db', database))
    """ :type: (objects.Provider) -> ObjectA """

    object_b = NewInstance(ObjectB,
                           InitArg('a', object_a),
                           InitArg('db', database))
    """ :type: (objects.Provider) -> ObjectB """


# Satisfaction of external dependency.
Catalog.database.satisfy(Singleton(sqlite3.Connection,
                                   InitArg('database', ':memory:'),
                                   Attribute('row_factory', sqlite3.Row)))

# Catalog static provides.
a1, a2 = Catalog.object_a(), Catalog.object_a()
b1, b2 = Catalog.object_b(), Catalog.object_b()

# Some asserts.
assert a1 is not a2
assert b1 is not b2
assert a1.db is a2.db is b1.db is b2.db is Catalog.database()