Wiring classes¶

Use constructor injection when the dependency belongs to the object's state. Decorate the class; it wires the constructor:

from typing import Annotated

from wireme import Wired, wire, wired


type DatabaseDep = Annotated[Database, wired(get_database)]


@wire
class TextProcessor:
    def __init__(self, *, database: DatabaseDep = Wired()) -> None:
        self._database = database

    def process(self, text: str) -> None:
        self._database.write(text)


TextProcessor().process("Hello from constructor injection")

The class decorator wires only the __init__ the class defines, and is equivalent to applying @wire to __init__ directly. It never scans or wraps other methods, so injection stays visible where it happens. A class without its own __init__ is rejected with a TypeError.

Use method injection when only a specific operation needs the dependency:

class TextProcessor:
    @wire
    def process(
        self,
        text: str,
        *,
        database: DatabaseDep = Wired(),
    ) -> None:
        database.write(text)


TextProcessor().process("Hello from method injection")

Constructor injection is useful for dependencies shared across multiple methods. Method injection keeps the object stateless when only one operation needs the dependency.

Runnable example¶

examples/classes.py

Next: The dependency graph