CODEWITHSUNDEEP
djangostringdjango-queryset
Krisnadi
Krisnadi

Reputation: 681

Django query update - the field is determined by a string

I want to update a record, but the field is determined by string. Is it possible to do so?

This is my model:

class Wallet(models.Model):
    user_id = models.IntegerField(blank=True, null=True)
    wallet1 = models.DecimalField(max_digits=15, decimal_places=2, blank=True, null=True)
    wallet2 = models.DecimalField(max_digits=15, decimal_places=2, blank=True, null=True)

This is my code:

amount = 200
transfer_from = 'wallet1'
transfer_to = 'wallet2'

obj = Wallet.objects.get(user_id=1)
obj.transfer_from = obj.transfer_from - amount
obj.transfer_to = obj.transfer_to + amount
obj.save()

Django only recognize the field when i write this:

obj.wallet1 = obj.wallet1 - amount

but it doesn't recognize this:

transfer_from = 'wallet1'
obj.transfer_from = obj.transfer_from - amount

Is said 'Wallet' object has no attribute 'transfer_from'. Thank you.

Upvotes: 1

Views: 1615

Answers (3)

vsd
vsd

Reputation: 1473

setattr(obj, transfer_form, getattr(obj, transfer_form) - amount)

getattr, setattr.

Upvotes: 1

Julien Salinas
Julien Salinas

Reputation: 1139

Actually this is a Python question. Please refer to this: What is getattr() exactly and how do I use it?

Using getattr, here is what you could do:

transfer_from_label = 'wallet1'
transfer_from = getattr(obj, transfer_from_label)
transfer_from = transfer_from - amount

Upvotes: 2

durdenk
durdenk

Reputation: 1660

This is not tested but should work.

amount = 200
transfer_from = 'wallet1'
transfer_to = 'wallet2'


obj = Wallet.objects.get(user_id=1)
transfer_from_field_val = getattr(obj,transfer_from)
transfer_to_field_val = getattr(obj,transfer_to)
transfer_from_field_val = transfer_from_field_val - amount
transfer_to_field_val = transfer_to_field_val + amount

setattr(obj , transfer_from, transfer_from_field_val)
setattr(obj , transfer_to, transfer_to_field_val)
obj.save()

Upvotes: 3

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