Django 使用save（）命令后未更新onetoonefied值

我试图从OneToOneField的默认值（None）更新它的值，但一切似乎都不起作用，因为当我调用save（）时，更改不会写入数据库。 相反，如果我从管理控制台更改值，一切都会正常工作

My models.py的外观如下所示：

class Payment(m.Model):
    [stuff...]

class Order(m.Model):
    [stuff...]
    active = m.BooleanField(default = False)
    payment = m.OneToOneField(Payment, null = True, blank = True, on_delete=m.SET_NULL)

def activate(self, ipn):
    [stuff..]
    self.payment = Payment(ipn = ipn)
    self.payment.save()
    self.active = True
    self.save()

ValueError: Cannot assign "...." instance isn't saved in the database.

我有一个激活订单的函数，如下所示：

class Payment(m.Model):
    [stuff...]

class Order(m.Model):
    [stuff...]
    active = m.BooleanField(default = False)
    payment = m.OneToOneField(Payment, null = True, blank = True, on_delete=m.SET_NULL)

def activate(self, ipn):
    [stuff..]
    self.payment = Payment(ipn = ipn)
    self.payment.save()
    self.active = True
    self.save()

ValueError: Cannot assign "...." instance isn't saved in the database.

在我对订单调用activate（）后，活动值将正确设置为True，但付款值仍保持为None。我想不出是怎么回事。有什么想法吗

---

Ps：如我所说，如果我从管理界面手动设置付款，一切都会正常。

当您将

付款

实例分配给

self.payment

时，会设置

付款id

。但是，

支付

实例在该点没有id。在将其分配给

OneToOneField

之前，需要先保存它

def activate(self, ipn):
    [stuff..]
    payment = Payment(ipn = ipn)
    payment.save()
    self.payment = payment
    self.active = True
    self.save()

def activate(self, ipn):
    [stuff..]
    payment = Payment(ipn = ipn)
    payment.save()
    self.payment = payment
    self.active = True
    self.save()

---

如果您尝试在shell中运行激活代码，您可能会看到如下内容：

class Payment(m.Model):
    [stuff...]

class Order(m.Model):
    [stuff...]
    active = m.BooleanField(default = False)
    payment = m.OneToOneField(Payment, null = True, blank = True, on_delete=m.SET_NULL)

def activate(self, ipn):
    [stuff..]
    self.payment = Payment(ipn = ipn)
    self.payment.save()
    self.active = True
    self.save()

ValueError: Cannot assign "...." instance isn't saved in the database.

因此，基本上首先需要创建一个

支付

实例：