在Django模型中添加一对多关系

Question

我的Django-REST应用程序中有两个模型。

一个ProjectRequest和一个ContactRequest

我想这样做，每个Projectrequest contains a list of the refered Contactrequests.

class ProjectRequest(models.Model):
project_name = models.CharField(max_length=50)
company_name = models.CharField(max_length=50)
#make array of technologiestechnologies = models.ArrayField(base_field=) (blank=True)
project_description = models.CharField(max_length=200)
project_type = models.CharField(max_length=30)
budget_estimation = models.IntegerField(
    default=1000,
    validators=[
    MinValueValidator(1800),
    MaxValueValidator(5000000)
])
#time_estimation = models.DateTimeField(default=None, blank=True, null=True)


class ContactRequest(models.Model):
topic = models.CharField(max_length=30)
description = models.CharField(max_length=200)
time = models.CharField(max_length=15)
project_request = models.ForeignKey(ProjectRequest, 
on_delete=models.CASCADE)

到目前为止，我已经与外键建立了关系，目前工作正常。但是，我想扩展功能，因此，ProjectRequest包含所有projectrequest的列表。我尝试了几个不同的领域，没有任何运气，文档我只能找到ManyToMany和OneToOne的字段。怎么能实现这一目标？

Answer 1

有很多方法可以达到你想要的效果。为此，我们在名为reverse relation的模型中添加contact_requests：

project_request = models.ForeignKey(ProjectRequest, on_delete=models.CASCADE, related_name="contact_requests")

现在你可以使用PrimaryKeyRelatedField来显示附加到每个ContactRequest的ProjectRequest的主键。

class ProjectRequestSerializer(serializers.ModelSerializer):
    contact_requests = serializers.PrimaryKeyRelatedField(many=True, read_only=True)

    class Meta:
        model = ProjectRequest
        fields = ('contact_requests', 'company_name', ...)  # other fields 

或者如果你想要每个contact_requests的所有值，那么你可以像这样使用nested relationship：

class ProjectRequestSerializer(serializers.ModelSerializer):
    contact_requests = ContactRequestSerializer(many=True, read_only=True)

    class Meta:
        model = ProjectRequest
        fields = ('contact_requests', 'company_name', ...) # and so on

Answer 2

您可以向Project Request类添加一个属性函数，该类返回与该ProjectRequest相关的所有Contact请求，如此...

class ProjectRequest(models.Model):
    project_name = models.CharField(max_length=50)
    company_name = models.CharField(max_length=50)
    #make array of technologiestechnologies = models.ArrayField(base_field=) (blank=True)
    project_description = models.CharField(max_length=200)
    project_type = models.CharField(max_length=30)
    budget_estimation = models.IntegerField(
        default=1000,
        validators=[
        MinValueValidator(1800),
        MaxValueValidator(5000000)
    ])
    #time_estimation = models.DateTimeField(default=None, blank=True, null=True)

    @property
    def contact_requests(self):
        return ContactRequest.objects.filter(project_request=self)


class ContactRequest(models.Model):
    topic = models.CharField(max_length=30)
    description = models.CharField(max_length=200)
    time = models.CharField(max_length=15)
    project_request = models.ForeignKey(ProjectRequest, 
    on_delete=models.CASCADE)