自动递增 Python Django model 中的文件

Question

This is my model

class Department(BaseModel):
    name = models.CharField(max_length=20, null=False)
    maximum_number_of_employees = models.PositiveIntegerField(MinValueValidator(0), MaxValueValidator(3))
    employee = models.ForeignKey(Employee, on_delete=models.CASCADE, null=False)

    def __str__(self):
        return self.name

I want to auto-increment the maximum_number_of_employees field upon the creation of the department and the associate of the employee to each department so that I can validate that the maximum_number_of_employees do not exceed the max limit

Answer 1

Override save method like this:

class Department(BaseModel):
    name = models.CharField(max_length=20, null=False)
    maximum_number_of_employees = models.PositiveIntegerField(MinValueValidator(0), MaxValueValidator(3))
    employee = models.ForeignKey(Employee, on_delete=models.CASCADE, null=False)

    def save(self, *args, **kwargs):
         if Department.objects.select_related('employee').count() < MAX_LIMIT: 
             self.maximum_number_of_employees += 1
             super(Department).save(self, *args, **kwargs)
         else:
             raise ValueError("Limit exceeded!")