Django, assigning a composite value to one field depending upon values entered in other fields in sa-CodePudding

I am new to django. What I am currently trying to do is set a value which is a primary key and non-editable automatically generated depending upon the values entered in the same model to some other fields. Here is an example:

   class Student(models.Model):
      student_id = models.CharField(max_length=100, primary_key=true)
      name  = models.CharField(max_length=100)
      class  = models.CharField(max_length=200)
      roll_no  = models.CharField(max_length=500)

So, what I am trying to achieve is if someone enters following information :

name = Haris
class = 8th
roll_no = 104011

The automatically generated primary key that would be non-editable for field "student_id" would be:

student_id = Haris_8th_104011

Does anyone have an idea how to achieve this? Hope my example made the query clear though.

CodePudding user response：

You can do this way overriding save method. Note that class variable clashesh with original builtin class name please migrate once as i changed the variable name

class Student(models.Model):
    student_id = models.CharField(max_length=100, primary_key=True, editable=False)
    name = models.CharField(max_length=100)

    classes = models.CharField(max_length=200)

    roll_no = models.CharField(max_length=500)

    def save(self, *args, **kwargs):
        self.student_id = f'{self.name}_{self.classes}_{self.roll_no}'
        super(Student,self).save(*args, **kwargs)