How can I define a django model's field default value to be another field value?-CodePudding

In my model I have these two fields:

start_bid = models.IntegerField(default=0)
max_bid =  models.IntegerField(default="the start_bid value")

The start_bid will be added by the user once through Django ModelForm. And the max_bid may change and may not. So I need the first value of 'max_bid' to be the start_bid value entered by the user, then if it changes it will be updated.

In brief, I need the initial value of max_bid to be equal to the start_bid!

Any suggestions?

CodePudding user response：

Overwrite save method on model.

def save(self, force_insert=False, force_update=False, using=None,  update_fields=None):  
        if self._state.adding: 
            self.max_bid = self.start_bid
        super().save(force_insert, force_update, using, update_fields)

CodePudding user response：

Here is the solution:

class Bid(models.Model):
          start_bid = models.IntegerField(default=0)
          max_bid =  models.IntegerField()
          
          def save(self,*args,**kwargs): 
               if not self.max_bid:
                   self.max_bid = self.start_bid   
                
               super(Bid,self).save(*args,**kwargs) #here Bid is my model name. Don't forget to replace Bid with your model name.