Django多对一

Question

我正在尝试在Django中创建一个简单的待办应用。我很难理解外键的概念。每个项目都假设要获得多个公寓，每个公寓应获得多个任务。

型号：

# Project model
class Project(models.Model):
    name = models.CharField(_("Name"), max_length=30)
    city = models.CharField(_("City"), max_length=30)
    street = models.CharField(_("Street"), max_length=30)
    number = models.IntegerField(_("Number"), max_length=4)
    ZIP = models.ImageField(_("ZIP"), max_length=10)
    manager = models.CharField(_("Manager"), choices=managers, default='ariel')

    # Apartments
    apartment = models.ForeignKey(_("Apartment"), Apartment, on_delete=models.CASCADE)

    def __repr__(self):
        return "{}".format(self.name)


# Apartment model
class Apartment(models.Model):
    building = models.CharField(_("Building"), max_length=4)
    floor = models.CharField(_("Floor"), max_length=4)
    number = models.CharField(_("Number"), max_length=4)
    type = models.CharField(_("Type"), max_length=4)
    upgraded = models.BooleanField(_("Upgraded"), default=False)
    drawing = models.FileField(_("Drawing"), upload_to=None)
    notes = models.TextField(_("Notes"), max_length=500)
    status = models.BooleanField(_("Completed"), default=False)

    # Tasks
    airTunnels = models.ForeignKey(_("Air Tunnels"), Task, on_delete=models.CASCADE)
    gasPipelines = models.ForeignKey(_("Gas Pipelines"), Task, on_delete=models.CASCADE)

    def __repr__(self):
        return "{} - {}".format(self.number, self.status)

# Task model
class Task(models.Model):
    title = models.CharField(_("Task"), max_length=30)
    doneBy = models.CharField(_("Done By"), choices=workers, default='daniel')
    date = models.DateTimeField(_("Date"), default=timezone.now())

    def __repr__(self):
        return "{}".format(self.title)

Answer 1

[如果使用apartment = models.ForeignKey(_("Apartment"), Apartment, on_delete=models.CASCADE)，则表示每个项目都有一个公寓。因此，您必须为每个公寓定义不同的项目。如果每个公寓只能有一个项目，则必须在公寓模型内定义外键，如下所示：

class Apartment(models.Model):
    #...your other fields
    project = models.ForeignKey(Project, on_delete=models.CASCADE)

对于公寓任务，如果我理解正确，您的公寓模型可以有多个任务。因此，您可以为此使用ManyToMany字段。有了此定义，每个公寓可以有多个任务。但是您的每个任务可以属于多个单元对象。如果您不希望每个任务都可以属于不同的单元对象，则必须设置OneToMany关系。可以通过向任务模型中添加foreignkeyfield来做到这一点：

class Task(models.Model):
    #...your other fields
    apartment = models.ForeignKey(Apartment, on_delete=models.CASCADE)