How to use FactoryAggregate in a container - aka Selector provider

Can I use FactoryAggregate in a DeclarativeContainer, where I choose the proper factory via config? The following code does not work

from dependency_injector import containers, providers


class A(object):
    name = "A"


class B:
    name = "B"


class C:
    def __init__(self, a_or_b):
        print(a_or_b.name)


class IoC(containers.DeclarativeContainer):
    config = providers.Configuration('config')
    aggregate_factory = providers.FactoryAggregate(a=providers.Factory(A), b=providers.Factory(B))
    # c_factory = providers.Factory(C, aggregate_factory('a')) # this works, but ignores the config
    c_factory = providers.Factory(C, aggregate_factory(config.a_or_b)) # this fails


def main():
    container = IoC(config={'a_or_b': 'a'})
    c = container.c_factory()


main()

[rmk135]

@githubkusi

The time has come.

I’ve added new Selector provider. It covers the case from this issue. It also supports Singleton or any other provider.

Code from the issue now can look like:

from dependency_injector import containers, providers


class IoC(containers.DeclarativeContainer):
    config = providers.Configuration('config')
    factory_selector = providers.Selector(config.a_or_b, a=providers.Singleton(A), b=providers.Singleton(B))
    c_factory = providers.Factory(C, factory_selector)


def main():
    container = IoC(config={'a_or_b': 'a'})
    c = container.c_factory()


if __name__ == '__main__':
    main()

• Selector provider is available since version 3.19. It’s already on PyPI.
• Here is a doc page for - Selector provider.

Thank you for bringing up the issue.

Roman

[rmk135]

That happens because FactoryAggregate provider can only accept Factory providers. This is a really dirty hack, but that’s how this could work if you need singletons:

class IoC(containers.DeclarativeContainer):
    config = providers.Configuration('config')
    aggregate_factory = providers.FactoryAggregate(
        a=providers.Factory(providers.Singleton(A)),
        b=providers.Factory(providers.Singleton(B)),
    )
    c_factory = providers.Factory(C, FactoryAggregateSelector(aggregate_factory, config.a_or_b))