ivankorobkov
commented
5 years ago Hi!
If a user forgets to bind a class to an instance, in the best case she gets an exception like TypeError for abstract classes, typing variables, callables that require at least one argument and so on. Such messages are usually not helpful and sometimes obscuring.
One can see DI from two different point of views: 1) DI allows to automatically instantiate a graph of interdependent service instances, which are a program. 2) DI allows to dynamically structure a program via late-binding of its dependencies.
I'm in favor of the first. Imagine a Twitter-like application:
class Config:
def __init__(self, dbconn=''):
self.dbconn = dbconn
class Db:
@inject.autoparams()
def __init__(self, config: Config):
pass
class Users:
@inject.autoparams()
def __init__(self, db: Db):
pass
class Tweets:
@inject.autoparams()
def __init__(self, db: Db, users: Users):
pass
class WsgiServer:
@inject.autoparams()
def __init__(self, tweets: Tweets, users: Users):
pass
In this case all dependencies are already specified. We only need to instantiate a graph of services with a custom Config:
def main():
config = Config.read_yaml("config.yaml")
inject.configure(lambda binder: binder.bind(Config, config))
# That's all!However, if you really need to prevent injector from automatically instantiating objects, I am not against it, but it will not be the default behaviour.
Also, please, update readme in the pull request.
o-fedorov
This addresses the issue #23