Django:如何通过自定义 Django_Admin 动态过滤外键选择

Question

我有三个模型:LineType、Service、DomainName、Record，它们之间有 m2m 或外键关系。这是代码:

class LineType(models.Model):
    linename = models.CharField(max_length=30,primary_key=True)

    def __unicode__(self):
        return self.linename

class Service(models.Model):
    servicename = models.CharField(max_length=30,primary_key=True)
    price = models.DecimalField(max_digits=8, decimal_places=2)
    line = models.ManyToManyField(LineType)

    def __unicode__(self):
        return self.servicename

class DomainName(models.Model):
    domainname = models.CharField(max_length=30,primary_key=True)
    user = models.ForeignKey(SiteProfile)
    service = models.ForeignKey(Service)

    def __str__(self):
        return self.domainname

class Record(models.Model):
    TYPE_CHOICES = (
                ('A','A'),
                ('CNAME','CNAME'),
                ('MX','MX'),
               )
    domainname = models.ForeignKey(DomainName)   

    def get_line(self):
        domain = DomainName.objects.get(pk=self.domainname_id)
        service = Service.objects.get(pk=domain.service_id)
        lines = service.line.all()
        choices = []
        for x in lines:
           choices.append((x.linename,x.linename))
        return choices

    host = models.CharField(max_length=30)
    type = models.CharField(max_length=5,choices=TYPE_CHOICES,default='A')
    line = models.ForeignKey(LineType)
    destaddress = models.CharField(max_length=30)

让我介绍一下模型。每个域名只能有一个服务，其他域名可以有。每个域名有多个记录。服务定义可应用于记录的 LineType。

我使用django admin来管理这些模型，但是Record中的“line”选择的都是LineType对象。所以问题是如何根据它的parent(DomainName)的“service”来过滤Record的LineType。

Answer 1

取决于您的确切要求和您的 Django 版本，答案可能是设置 limit_choices_to attribute of the foreign key ，或自定义 ModelAdmin 表单:

使用 limit_choices_to
只需将线路选择限制为那些匹配的 linename == 'foo'

class Record(models.Model):
    # ...
    line = models.ForeignKey(LineType, limit_choices_to={'linename': 'foo'}))

使用自定义 form
如果实例化表单时存在实例，我们可以选择它的域服务行作为查询集选择

class RecordAdminForm(forms.ModelForm):
    def __init__(self, *args, **kwargs):
        super(RecordAdminForm, self).__init__(*args, **kwargs)

        # access object through self.instance...
        if self.instance:
            valid_lines = self.instance.domainname.service.line.objects.all()
            self.fields['line'].queryset = valid_lines

class RecordAdmin(admin.ModelAdmin):
    form = RecordAdminForm
    # ...

引用SO问题:

how to limit the foreignkey dropdown with constraints?

How do I filter ForeignKey choices in a Django ModelForm?