wint 0.2.0

Dependency injection with type hints

Wint - dependency injection with type hints.

Intro

Wint is a lightweight library that implements dependency injection via type hinting.

Installation

Just use pip:

$ pip install wint

How it works

There are a ton of approaches to DI, and this library implements only property injection.

When autowired decorator is applied then class is inspected for all annotated properties. If property has no value, then it is replaced with DependencyDescriptor.

Dependency is resolved when attribute is accessed on instantiated class instance.

This behaviour allows to resolve dependencies in lazy manner with the downside of a side effect — instance receives a descriptor property that was not existed earlier.

Example

from wint import autowired, ContainerProvider


class Printer:
    """Abstract class for printing messages."""

    def print(self, message):
        raise NotImplementedError


class RealPrinter(Printer):
    """Implementation of `Printer` which uses `print` to output messages."""

    def print(self, message):
        print(message)


@autowired()
class PrintService:
    # RealPrinter will be automatically injected on property access.
    printer: Printer

    def run(self, msg):
        self.printer.print(f"{msg}, i'm running!")


if __name__ == "__main__":
    container = ContainerProvider.get()
    # Register RealPrinter as singleton implementation of Printer.
    container.register(Printer, RealPrinter())

    PrintService().run('hey')

$ python example.py
hey, i'm running!

Notes

This library is built on punq (MIT License) and uses it's vendored version.