CODEWITHSUNDEEP
djangopython-2.7django-rest-framework
Dean
Dean

Reputation: 1236

In Django REST framework, how do you access a field in a table referenced by a foreign key

I have the following models in Django:

class campaign(models.Model):
    start_date = models.DateField('Start Date')
    end_date = models.DateField('End Date')
    description = models.CharField(max_length=500)
    name = models.CharField(max_length=200)
    active_start_time = models.TimeField()
    active_end_time = models.TimeField()
    last_updated = models.DateTimeField('Date updated',auto_now=True)
    active = models.BooleanField(default=True)
    client_id = models.ForeignKey('client',on_delete=models.PROTECT)
    def __unicode__(self):
            return u'%d | %s | %s' % (self.id,self.name, self.description)

class campaign_product(models.Model):
    product_id = models.ForeignKey('product',on_delete=models.PROTECT)
    last_updated = models.DateTimeField('Date updated',auto_now=True)
    campaign_id = models.ForeignKey('campaign',on_delete=models.PROTECT)

class product(models.Model):
    name = models.CharField(max_length=200)
    description = models.CharField(max_length=500)
    sku = models.CharField(max_length=200,blank=True,null=True)
    retail_price = models.DecimalField(decimal_places=2,max_digits=11)
    discount_price = ((1,'Yes'),(0,'No'))
    discounted_price = models.DecimalField(decimal_places=2,max_digits=11,blank=True,null=True)
    category_id = models.ForeignKey('category',on_delete=models.PROTECT)
    last_updated = models.DateTimeField('Date updated',auto_now=True)
    active = models.BooleanField(default=True)
    def __unicode__(self):
        return u'%d | %s' % (self.id, self.name)

I also have the following serializer:

class campaignProductSerializer(serializers.HyperlinkedModelSerializer):
    class Meta:
        model = campaign_product
        fields = ('product_id', 'campaign_id')

And the following view set behavior in the urls.py file:

class campaignProductViewSet(viewsets.ModelViewSet):
    queryset = campaign_product.objects.filter(campaign_id__start_date__lte=datetime.now(),campaign_id__end_date__gte=datetime.now(),campaign_id__active__exact=True)
    serializer_class = campaignProductSerializer

My problem is I need to include the name field from the products model in my query results when for instance a request is made on http://127.0.0.1:8000/campaign_product/1/. Currenly this request returns only the product_id and the campaign_id. I tried making the serializer as follows:

class campaignProductSerializer(serializers.HyperlinkedModelSerializer):
    class Meta:
        model = campaign_product
        fields = ('product_id', 'campaign_id', 'product.name')

But then the service returns the following error:

Field name `product.name` is not valid for model `campaign_product`.

I event tried using product__name with and without quotes. Without quotes it tells me that there is no such variable, and with quotes it gives the is not valid for model error similar to the above. Heeelp! Getting this extra field is proving to be a pain :-(

Upvotes: 0

Views: 230

Answers (1)

Joey Wilhelm
Joey Wilhelm

Reputation: 5819

What you want will need to look something more like this:

class campaignProductSerializer(serializers.HyperlinkedModelSerializer):
    product_name = serializers.CharField(source='product_id.name')

    class Meta:
        model = campaign_product
        fields = ('product_id', 'campaign_id', 'product_name')

P.S. As an unrelated side note, it is generally a convention in Python code to name classes with CamelCase, such as Campaign, CampaignProduct, Product, and CampaignProductSerializer.

Edit: P.P.S. Originally, I had put written the product_name field with source='product.name'. This was actually due to me looking at the code too quickly and making assumptions based on Django conventions. Typically, with a Django ForeignKey, you would name the ForeignKey field after the model you are linking to, rather than explicitly naming it with _id. For example, the CampaignProduct model would typically be written with product = ForeignKey(...) and campaign = ForeignKey(...). In the background, Django will actually use product_id and campaign_id as the database field names. You also have access to those names on your model instances. But the product and campaign variables on your model instances actually return the objects which you are referring to. Hopefully that all makes sense.

Upvotes: 4

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