"""`AbstractFactory` providers example.""" import abc import dataclasses import random from typing import List from dependency_injector import 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 cache_client_factory = providers.AbstractFactory(AbstractCacheClient) service_factory = providers.Factory( Service, cache=cache_client_factory, ) if __name__ == '__main__': cache_type = random.choice(['redis', 'memcached', None]) if cache_type == 'redis': cache_client_factory.override( providers.Factory( RedisCacheClient, host='localhost', port=6379, db=0, ), ) elif cache_type == 'memcached': cache_client_factory.override( providers.Factory( MemcachedCacheClient, hosts=['10.0.1.1'], port=11211, prefix='my_app', ), ) service = 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() must be # overridden before calling