Dependency Injection

AppUnit provides Dependency Injection mechanism which allows the creation of dependent objects outside of a class and provides those objects to a class through different way using Injector framework.

Bindings

You can set and get application dependencies using bind and lookup methods.

from appunit.applications import AppUnit

app = AppUnit()
app.bind(str, to="Hello DI!")

print(app.lookup(str))

Output:

Hello DI!

Scopes

You can also provide different scopes to your dependencies.

No Scope

from appunit.applications import AppUnit

app = AppUnit()
app.bind(str, to="Hello DI!")

print(app.lookup(str))

Singleton

Defining binding with singleton scope means the container creates a single instance of that binding, and all requests for that binding interface will return the same object, which is cached.

from injector import SingletonScope

from appunit.applications import AppUnit


class Component:
    def __init__(self, name: str):
        self.name = name


app = AppUnit()
app.bind(Component, to=Component("db"), scope=SingletonScope)

print(app.lookup(Component))

Request

Defining binding with request scope means the container creates a single instance of that binding for every request which is cached.

from injector import inject
from starlette.requests import Request

from appunit.applications import AppUnit
from appunit.dependencies import RequestScope


class Path(str):
    pass


@inject
def get_path(request: Request) -> Path:
    return Path(request.url.path)


app = AppUnit()
app.bind(Path, to=get_path, scope=RequestScope)


@app.get("/")
def index(path: Path):
    return f"path is `{path}`"


if __name__ == "__main__":
    app.run()

inject decorator declaring parameters to be injected.