How to implement this logic in Django models?

Using Django
1

class Scheme(models.Model):
class Type(models.TextChoices):
OPEN = ‘OPEN’, ‘OPEN’
CLOSE = ‘CLOSE’, ‘CLOSE’

if Type.choices == Type.Close:
  {a DateField should appear such as maturity_date}
else
  {no field for maturity_date}
2

I would consider doing something like this:

from datetime import datetime

class Scheme(models.Model):
    class Types(models.TextChoices):
        OPEN = "OPEN", "OPEN"
        CLOSE = "CLOSE", "CLOSE"

    type = models.CharField(
        max_length=50, choices=Types.choices, default=Types.OPEN
    )
    # We can't have attributes determined by if statements. If a model
    # has an attribute, then it always has that attribute. It can however be None
    # the default value for the below is None
    maturity_date = models.DateField(default=None, null=True, blank=True)

    # this method runs everytime an instance of Scheme is saved
    def save(self, *args, **kwargs):
        if self.type == self.Types.CLOSE and self.maturity_date is not None:
            self.maturity_date = datetime.now()
        return super().save(*args, **kwargs)

In essence, we have a model with a datetime field which is by default None. When save is called on an instance of Scheme , save() is run and will check if the instance’s type is CLOSED and if its time value is None. If these conditions are met, then maturity_date will be assigned the value of datetime.datetime.now(). If the conditions are not met, then maturity_date remains as it was, either None or the timestamp of when it was first stamped.

Hope this helps you on your way.

3

Thanks conor,
This solution seems to be working, but the only thing I am facing now is that maturity_date field is auto filled with current date when it’s close type. I want to post maturity_date for close type, instead of datetime.now.

4

You’re welcome. If you want to create the maturity_date with a POST request and not have it created automatically then you can remove the save() method and just let the base class save() method do its thing.