Get Started

Install injectme

pip install injectme

Use it in your project

Let’s start with simple project:

.
└── src
    ├── bootstrap.py
    ├── repositories.py
    └── services.py

Contents of src/repositories.py

class UsersRepository:
    def __init__(self, users):
        self.users = users

    def get_users(self):
        return self.users


class CarsRepository:
    def __init__(self, cars):
        self.cars = cars

    def get_cars(self):
        return self.cars

Contents of src/services.py

from .repositories import (
    CarsRepository,
    UsersRepository,
)


class CarsService:
    def __init__(self, cars_repo: CarsRepository):
        self.cars_repo = cars_repo

    def show_cars(self):
        print(self.cars_repo.get_cars())


class UsersService:
    def __init__(self, users_repo: UsersRepository):
        self.users_repo = users_repo

    def show_users(self):
        print(self.users_repo.get_users())


class RentalService:
    def __init__(
        self,
        cars_repo: CarsRepository,
        users_repo: UsersRepository,
    ):
        self.cars_repo = cars_repo
        self.users_repo = users_repo

    def rent(self):
        print(self.cars_repo.get_cars())
        print(self.users_repo.get_users())

Contents of src/bootstrap.py

from .repositories import CarsRepository, UsersRepository
from .services import (
    CarsService,
    UsersService,
    RentalService,
)

cars_repository = CarsRepository(("cara", "carb"))
users_repository = UsersRepository(("usera", "userb"))

cars_service = CarsService(cars_repository)
users_service = UsersService(users_repository)
rental_service = RentalService(
    cars_repo=cars_repository,
    users_repo=users_repository,
)

There is no much code in here so it does not look that bad. Be aware though that this is dummy example. With real-life project you would end up with a lot more of dependency handling during bootstrap phase.

Now let’s see how it looks like with injectme. Using the same project, we can improve on the dependency management part like this:

Contents of src/services.py

from injectme import inject

from .repositories import (
    CarsRepository,
    UsersRepository,
)


@inject
class CarsService:
    cars_repo: CarsRepository

    def show_cars(self):
        print(self.cars_repo.get_cars())


@inject
class UsersService:
    users_repo: UsersRepository

    def show_users(self):
        print(self.users_repo.get_users())


@inject
class RentalService:
    cars_repo: CarsRepository
    users_repo: UsersRepository

    def rent(self):
        print(self.cars_repo.get_cars())
        print(self.users_repo.get_users())

Contents of src/bootstrap.py

from injectme import register

from .repositories import CarsRepository, UsersRepository
from .services import (
    CarsService,
    UsersService,
    RentalService,
)

register(CarsRepository, CarsRepository(("cara", "carb")))
register(UsersRepository, UsersRepository(("usera", "userb")))

cars_service = CarsService()
users_service = UsersService()
rental_service = RentalService()

Pay attention to the *Service classes. All of them have been decorated with @inject decorator. It marks them as targets for “injection”. The dependencies required by a class decoreated with @inject are specified as annotations (e.g. cars_repo: CarsRepository). Each annotation will become an attribute of class’s instance.

Note

In the example with injectme there are no changes to the src/repositories.py file so it’s not included. Don’t get fooled by reduced amount of code.