ioc.py

mport inspect


class Container(object):

  def __init__(self):
    self.registry = {}

  def register(self, interface, implementation):
    self.registry[interface.__name__] = implementation

  def resolve(self, entity):
    if entity.__name__ in self.registry:
      creator = self.registry[entity.__name__]
    else:
      creator = entity

    init_func = creator.__init__
    arg_spec = inspect.getfullargspec(init_func)
    arg = arg_spec.args.copy()
    arg.remove('self')

    if len(arg) == 0:
      return entity()
    if len(arg) != len(arg_spec.annotations):
      raise ValueError('missing annotations for arguments')

    init_args = {}
    for argname, interface in arg_spec.annotations.items():
      if interface.__name__ in self.registry:
        implementation = self.registry[interface.__name__]
        impl_instance = self.resolve(implementation)
        init_args[argname] = impl_instance

    return entity(**init_args)


if __name__ == '__main__':

  class ICallable(object):
    pass


  class ConcreteCallable(object):
    def call(self):
      return 1

  class Consumer(object):
    def __init__(self, c: ICallable):
      self.c = c

  container = Container()
  container.register(ICallable, ConcreteCallable)

  cc = container.resolve(ConcreteCallable)

  print(cc.call())