gistfile1.txt

def test_weak_and_lazy_loading():
    '''Test loading/saving of model references'''

    class ChainMember(Model):
        '''This is a simple infinite chain of models referencing each other.'''

        def __init__(self, number, prev_member=None, next_member=None):
            Model.__init__(self)
            self.number = number
            self.prev_member = ref(prev_member, prev_member.model_id if prev_member is not None else None)
            self.next_member = ref(next_member, next_member.model_id if next_member is not None else None)

        @weak_and_lazy
        def prev_member(self, model_id):
            try:
                return self.loader.load(model_id)
            except KeyError:
                new_chain = ChainMember(self.number - 1, None, self)
                self.loader.register(new_chain)
                return new_chain

        @weak_and_lazy
        def next_member(self, model_id):
            try:
                return self.loader.load(model_id)
            except KeyError:
                new_chain = ChainMember(self.number + 1, self, None)
                self.loader.register(new_chain)
                return new_chain

    # Instantiate loader
    loader = DefaultLoader()

    # Create a chain and register it
    c1 = ChainMember(1)
    loader.register(c1)

    # Obtain more members
    c2 = c1.next_member
    assert c2.number == 2
    c3 = c2.next_member
    assert c3.prev_member is c1.next_member

    # Test the loading from the backend by asserting identity after deleting
    # the second chain member
    print c2
    del c2
    print id(c3.prev_member)
    print id(c1.next_member)
    assert c3.prev_member is c1.next_member