Python Django QuerySet 猴子修补以向返回的模型添加新属性

您可以将QuerySet子类化以实现apply_some_function_to_monkey_patch，并重写_fetch_all以运行回调函数，类似于QuerySet.prefetch_related是implemented.您还需要重写__init__和_clone以使其与过滤器一起工作.

class MyQuerySet(models.QuerySet):
    def __init__(self, model=None, query=None, using=None, hints=None):
        super().__init__(model=model, query=query, using=using, hints=hints)
        self._callback_funcs = ()
        self._callback_done = False

    def apply_some_function_to_monkey_patch(self, *callback_funcs):
        qs = self._chain()
        qs._callback_funcs = qs._callback_funcs + callback_funcs
        return qs

    def _callback(self):
        for callback_func in self._callback_funcs:
            for item in self._result_cache:
                callback_func(item)
        self._callback_done = True

    def _clone(self):
        clone = super()._clone()
        clone._callback_funcs = self._callback_funcs[:]
        return clone

    def _fetch_all(self):
        super()._fetch_all()
        if self._callback_funcs and not self._callback_done:
            self._callback()

用法:

class MyManager(BaseManager.from_queryset(MyQuerySet)):
    pass


class MyModel(models.Model):
    objects = MyManager()

def callback_func(instance):
    instance.last_values_dict = json.loads(instance.last_valid_field_values)
    
    
MyModel.objects.all().apply_some_function_to_monkey_patch(callback_func)