Question

我想更新记录，但该字段由字符串确定。是否可以这样做？

这是我的模特：

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)

这是我的代码：

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()

当我写这个时，Django只识别该字段：

obj.wallet1 = obj.wallet1 - amount

但它不承认这一点：

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

说“钱包”对象没有属性“transfer_from”。谢谢。

Answer 1

实际上这是一个Python问题。请参阅：What is getattr() exactly and how do I use it?

使用getattr，您可以执行以下操作：

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

Answer 2

这未经过测试但应该有效。

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()

Answer 3

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

getattr，setattr。

Django查询更新 - 字段由字符串确定

3 个答案: