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在节省数据库费用之前与会议合作
原标题:Work with instance in session before save in database

I have a system with several steps. Each step increments one single object instance. I want to save the instance in db only in the final step, on others just update the instance I saved in the session.

My model class seems like this:

class Proposta(models.Model):
    Modelo = models.ForeignKey("ModeloVersao", verbose_name="Modelo")
    Pacotes = models.ManyToManyField("PacoteModelo", null=True, blank=True)
    Opcionais = models.ManyToManyField("ItemModelo", null=True, blank=True)
    RevestimentoInterno = models.ForeignKey("RevestimentoInternoModelo", verbose_name="Revestimento Interno")
    Cor = models.ForeignKey("CorModelo")
    CorSecundaria = models.ForeignKey("CorModeloSecundaria", verbose_name="Cor secundária", null=True, blank=True)
    Data = models.DateTimeField(auto_now_add = True)
    Status = models.CharField("Status", choices=STATUS_PROPOSTA, max_length=10)
    Cliente = models.ForeignKey("Cliente")

Here s my problem: When I try to add or retrieve m2m fields it obviously throws a ValueError with the message Proposta instance needs to have a primary key value before a many-to-many relationship can be used.

我成功地取得了希望的结果,用pk=0制造了我的肥胖症,但我相信,如果有的话,那是最好的。

这样做的方法不像这样。

任何帮助都是巨大的。

增 编

最佳回答

您可以找到以下答案:https://stackoverflow.com/questions/518162/how-to-work-with-unsaved-many-to-many-relations-in-django”。

快速参考摘要:

我不妨补充,文件在解释save(> 方法

Of those, I recommend using ModelForms. Hopefully this helps!

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