如何使 boolean 字段在 Django 中只保留一个真值

Question

Am working on a Saving scheme, I have implemented it so that it works on cycles.

Is there a way I can have only one active cycle enforced by my boolean field?

models.py

class Cycle(models.Model):
    cycle_name =  models.CharField( max_length=220, null=True, blank=True, unique=True)
    rate = models.IntegerField(default=15, null=True, blank=True)
    cycle_period_start = models.DateField(max_length=255, blank=False, null=False, unique=True)
    cycle_period_end = models.DateField(max_length=255, blank=False, null=False, unique=True)
    is_active = models.BooleanField(default=True) 

    def __str__(self):
        return self.cycle_period_start.year + "/" + self.cycle_period_end.year

Basically what I want is that when I add new cycle, the field is_active is set to False for other cycle.

Thank you for the help

Answer 1

So what you could do is before creating the new Cycle is to update all existing cycles that the are no longer active.

Thus something like this.

Cycle.objects.update(is_active=False)
Cycle.objects.create(is_active=True, ...)