aioinject 0.5.0

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Async-first dependency injection library based on python type hints

Quickstart

First let's create a class we would be injecting:

class Service:
    pass

Then we should create instance of container and register Service class in it using a provider:

from aioinject import Container, providers

container = Container()
container.register(providers.Callable(Service))

Then we can create a context and resolve our Service class from it:

with container.sync_context() as ctx:
    service = ctx.resolve(Service)

If you need to inject something into a function just annotate it with inject:

from aioinject import inject


@inject
def awesome_function(service: Service):
    print(service)

And call it within an active context:

with container.sync_conext() as ctx:
    awesome_function()

Complete example (should run as-is):

from typing import Annotated

from aioinject import Container, Inject, inject, providers


class Service:
    pass


container = Container()
container.register(providers.Callable(Service))


@inject
def awesome_function(
    service: Service,
):
    print(service)


with container.sync_context() as ctx:
    service = ctx.resolve(Service)
    awesome_function()

Specifying Dependencies

To mark parameters for injection we can use typing.Annotated and Inject marker

from typing import Annotated
from aioinject import Callable, Container, Inject


class Session:
    pass


class Service:
    def __init__(self, session: Session):
        self.session = session


container = Container()
container.register(Callable(Session))
container.register(Callable(Service))

with container.sync_context() as ctx:
    service = ctx.resolve(Service)

If you have multiple dependencies with same type you can specify concrete implementation in Inject:

import dataclasses
from typing import Annotated

from aioinject import Container, providers, inject, Inject


@dataclasses.dataclass
class Client:
    name: str


def get_github_client() -> Client:
    return Client(name="GitHub Client")


def get_gitlab_client() -> Client:
    return Client(name="GitLab Client")


container = Container()
container.register(providers.Callable(get_github_client))
container.register(providers.Callable(get_gitlab_client))


@inject
def injectee(
    github_client: Annotated[Client, Inject(get_github_client)],
    gitlab_client: Annotated[Client, Inject(get_gitlab_client)],
):
    print(github_client, gitlab_client)


with container.sync_context() as ctx:
    # Manually resolving client
    client = ctx.resolve(Client, impl=get_github_client)
    print(client)
    injectee()

Working with Resources

Often you need to initialize and close a resource (file, database session, etc...), you can do that by using a contextmanager that would return your resource.
We would use custom Session class that defines __exit__ and __enter__ methods:

import contextlib

from aioinject import Container, providers


class Session:
    def __init__(self):
        self.closed = False

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.closed = True


@contextlib.contextmanager
def get_session() -> Session:
    with Session() as session:
        yield session


container = Container()
container.register(providers.Callable(get_session))

with container.sync_context() as ctx:
    session = ctx.resolve(Session)
    print(session.closed)
print(session.closed)  # <- Session.__exit__ would be called when context closes

Async Dependencies

You can register async resolvers the same way as you do with other dependencies, all you need to change is to use Container.context instead of Container.sync_context:

import asyncio

from aioinject import Container, providers


class Service:
    pass


async def get_service() -> Service:
    await asyncio.sleep(1)
    return Service()


async def main():
    container = Container()
    container.register(providers.Callable(get_service))

    async with container.context() as ctx:
        service = await ctx.resolve(Service)
        print(service)


if __name__ == '__main__':
    asyncio.run(main())

Providers

When creating a provider you should specify the type it returns, but it can be inferred from class type or function return type:

Callable

Callable provider would create instance of a class each time:

from aioinject import Callable


class Service:
    pass


provider = Callable(Service)
service_one = provider.provide_sync()
service_two = provider.provide_sync()
print(service_one is service_two)
# False

Singleton

Singleton works the same way as Callable but it caches first created object:

from aioinject import Singleton


class Service:
    pass


provider = Singleton(Service)
first = provider.provide_sync()
second = provider.provide_sync()
print(first is second)
# True

Object

Object provider just returns an object provided to it:

from aioinject import Object


class Service:
    pass


provider = Object(Service())
service = provider.provide_sync()
print(service)
# <__main__.Service>