识别 django post_save 信号中更改的字段 [英] Identify the changed fields in django post_save signal

问题描述

我正在使用 django 的 post_save 信号在保存模型后执行一些语句.

I'm using django's post_save signal to execute some statements after saving the model.

class Mode(models.Model):
    name = models.CharField(max_length=5)
    mode = models.BooleanField()


from django.db.models.signals import post_save
from django.dispatch import receiver

@receiver(post_save, sender=Mode)
def post_save(sender, instance, created, **kwargs):
        # do some stuff
        pass

现在我想根据mode字段的值是否改变来执行一个语句.

Now I want to execute a statement based on whether the value of the mode field has changed or not.

@receiver(post_save, sender=Mode)
def post_save(sender, instance, created, **kwargs):
        # if value of `mode` has changed:
        #  then do this
        # else:
        #  do that
        pass

我查看了一些 SOF 主题和博客，但找不到解决方案.他们所有人都试图使用 pre_save 方法或表单，这不是我的用例.https://docs.djangoproject.com/es/1.9/ref/django 文档中的信号/#post-save 没有提到直接的方法.

I looked at a few SOF threads and a blog but couldn't find a solution to this. All of them were trying to use the pre_save method or form which are not my use case. https://docs.djangoproject.com/es/1.9/ref/signals/#post-save in the django docs doesn't mention a direct way to do this.

下面链接中的答案看起来很有希望，但我不知道如何使用它.我不确定最新的django版本是否支持它，因为我使用ipdb来调试这个，发现instance变量没有属性has_changed 如以下答案中所述.

An answer in the link below looks promising but I don't know how to use it. I'm not sure if the latest django version supports it or not, because I used ipdb to debug this and found that the instance variable has no attribute has_changed as mentioned in the below answer.

Django: 保存时，如何查看字段是否发生变化?

推荐答案

将其设置在模型的 __init__ 上，以便您可以访问它.

Set it up on the __init__ of your model so you'll have access to it.

def __init__(self, *args, **kwargs):
    super(YourModel, self).__init__(*args, **kwargs)
    self.__original_mode = self.mode

现在您可以执行以下操作:

Now you can perform something like:

if instance.mode != instance.__original_mode:
    # do something useful

这篇关于识别 django post_save 信号中更改的字段的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！