python-dependency-injector/examples/providers/abstract_factory.py

"""`AbstractFactory` providers example."""

import abc
import dataclasses
import random
from typing import List

from dependency_injector import containers, providers


class AbstractCacheClient(metaclass=abc.ABCMeta):
    ...


@dataclasses.dataclass
class RedisCacheClient(AbstractCacheClient):
    host: str
    port: int
    db: int


@dataclasses.dataclass
class MemcachedCacheClient(AbstractCacheClient):
    hosts: List[str]
    port: int
    prefix: str


@dataclasses.dataclass
class Service:
    cache: AbstractCacheClient


class Container(containers.DeclarativeContainer):

    cache_client_factory = providers.AbstractFactory(AbstractCacheClient)

    service_factory = providers.Factory(
        Service,
        cache=cache_client_factory,
    )


if __name__ == "__main__":
    container = Container()

    cache_type = random.choice(["redis", "memcached"])
    if cache_type == "redis":
        container.cache_client_factory.override(
            providers.Factory(
                RedisCacheClient,
                host="localhost",
                port=6379,
                db=0,
            ),
        )
    elif cache_type == "memcached":
        container.cache_client_factory.override(
            providers.Factory(
                MemcachedCacheClient,
                hosts=["10.0.1.1"],
                port=11211,
                prefix="my_app",
            ),
        )

    service = container.service_factory()
    print(service.cache)
    # The output depends on cache_type variable value.
    #
    # If the value is "redis":
    # RedisCacheClient(host="localhost", port=6379, db=0)
    #
    # If the value is "memcached":
    # MemcachedCacheClient(hosts=["10.0.1.1"], port=11211, prefix="my_app")
    #
    # If the value is None:
    # Error: AbstractFactory(<class "__main__.AbstractCacheClient">) must be
    # overridden before calling