Inheritance

It is possible to use class marked as a target for injection as a parent class in inheritance. If you want to add additional dependencies in the child class, it’s possible. The only requirement is that both parent and child are decorated by the injectme.inject() or injectme.Injector.

The parent’s dependencies are available to child as if they were its own attributes. It’s good to take a look at the __init__ guide to better understand how this mechanism works.

Example:

example.py

from injectme import inject, register


class DependencyA:
    def __init__(self, name):
        self.name = name

    def __str__(self):
        return f"DependencyA: {self.name}"


class DependencyB:
    def __init__(self, name):
        self.name = name

    def __str__(self):
        return f"DependencyB: {self.name}"


# base class has to be decorated using Injector
@inject
class BaseService:
    dep_a: DependencyA


# derived class also needs to be decorated by Injector
@inject
class AdvancedService(BaseService):
    dep_b: DependencyB

    def print_deps(self):
        print("AdvancedService deps:")
        print(self.dep_a)
        print(self.dep_b)


# register dependencies
register(DependencyA, DependencyA("Alice"))
register(DependencyB, DependencyB("Bob"))

advanced_service = AdvancedService()
advanced_service.print_deps()

$ python3 example.py

AdvancedService deps:
DependencyA: Alice
DependencyB: Bob