兩種方法檢查模型中某個(gè)字段發(fā)生改變

How to check if a filed has changed when model save

Django 2.1.7

1. 在模型中檢查

適用于在任何時(shí)候字段發(fā)生變化采取動(dòng)作

class Task(models.Model):
    if_done = models.BooleanField('If Done', default=False)
    __original_done = None
    
    
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        # inital original
        self.__original_done = self.if_done

    def save(self, *args, **kwargs):
        if not self.__original_done and self.if_done:
            # if_done changed, do something
            
        super().save(*args, **kwargs)
        # update the original
        self.__original_done = self.if_done

2. 在 Admin Class 中檢查

適用于只在使用admin的時(shí)候檢查字段變化，
由于寫(xiě)在了admin class 里，所以如果有其他views 修改了改model，檢查是不起作用的。

利用 Form.changed_data 值檢查

class TaskAdmin(admin.ModelAdmin):

    def save_model(self, request, obj, form, change):
        if 'if_done' in form.changed_data:
            messages.info(request, "The task status has changed")
        else:
            messages.info(request, "The task status has not changed")
        super().save_model(request, obj, form, change)