events.py 文件源码

def _listen(cls, target, identifier, fn,
                            raw=False, retval=False, propagate=False):

        if not raw or not retval:
            if not raw:
                meth = getattr(cls, identifier)
                try:
                    target_index = \
                        inspect.getargspec(meth)[0].index('target') - 1
                except ValueError:
                    target_index = None

            wrapped_fn = fn

            def wrap(*arg, **kw):
                if not raw and target_index is not None:
                    arg = list(arg)
                    arg[target_index] = arg[target_index].obj()
                if not retval:
                    wrapped_fn(*arg, **kw)
                    return orm.interfaces.EXT_CONTINUE
                else:
                    return wrapped_fn(*arg, **kw)
            fn = wrap

        if propagate:
            for mapper in target.self_and_descendants:
                event.Events._listen(mapper, identifier, fn, propagate=True)
        else:
            event.Events._listen(target, identifier, fn)