Django Rest Serializer: Reverse relationships

Question

Disclaimer: I am learning django as I apply it to a database / PHP app i inherited. The database is a bit of a mess, with no foreign key constrains, and inconsistent naming. I do not want to touch or redo anything on the database because I don't want to mes with the legacy application at all.

Stack: Python 2.7. Django 1.5, Django Rest Framework

The problem is that I have a relationship where there is an Idea that has multiple Tickers. The tickers table has the foreign key to the ideas (teaser_id) so that we have something like

**Tickers**
id teaser_id 
1  1
2  1
3  1
4  2
4  2 

**Ideas**
id
1
2

I had django generate the model from the database, but without the FK Constraints it didn't generate all the relationships properly. So here is haw the models are configured:

class Tickers(models.Model):
    id = models.IntegerField(primary_key=True)

    # I changed to this
    teaser_id = models.ForeignKey(Idea)
    # From        
    # teaser_id = models.IntegerField(null=True, blank=True)

    ticker = models.CharField(max_length=135L, blank=True)
    date_added = models.CharField(max_length=135L, blank=True)
    class Meta:
        db_table = 'teaser_tickers'


class Idea(models.Model):
    id = models.IntegerField(primary_key=True)
    industry_id = models.IntegerField()
    post_type = models.CharField(max_length=45L)

    class Meta:
        db_table = 'idea'

Here are my serializers

class TickerSerializer(serializers.HyperlinkedModelSerializer):

    class Meta:
        model = myModels.Tickers
        fields = (
            'id'
            ,'teaser_id'
            ,'ticker'
        )

class IdeaSerializer(serializers.HyperlinkedModelSerializer):
    user = UserSerializer(many=False, read_only=True)
    ticker = TickerSerializer(many=True, read_only=True, )
    teaser = myFields.TeaserField(teaser_length=200, original_field='content')

    class Meta:
        model = myModels.Idea
        fields = (
            'id'
            , 'title'
            , 'date_added'
            , 'user'
            , 'teaser'
            , 'ticker'
        )

I want the Ideas Resource to return the tickers as a child node set.

The REST request is for the Idea where the tickers is a child element. So I am getting an exception that ticker isn't defined in idea. Fine get that - but I am just guessing on how to set this up at this point - I am sludging through documentation and source - but was hoping someone could help me out.

THank you

Answer 1

As akaphenom said you have to use the related_name in your serializer, but since you don't specify any in your models you must use the default, in this case teaser_set and your IdeaSerializer must be:

class IdeaSerializer(serializers.HyperlinkedModelSerializer):
    user = UserSerializer(many=False, read_only=True)
    tickers = ReverseTickerSerializer(many=True, read_only=True)
    teaser_set = myFields.TeaserField(teaser_length=200, original_field='content')


class Meta:
    model = myModels.Idea
    fields = (
        'id',
        'title',
        'date_added',
        'user',
        'teaser_set',
        'tickers',
    )

Answer 2

SO the solution for the reverse lookup is specifying the model correctly, and namely the related_name which is the field that is created in the foreign model to perform the reverse look up. Now I specified a custom serializer to limit to the content I am interested in - but that piece is optional.

class Tickers(models.Model):
    id = models.IntegerField(primary_key=True)

    # I changed to this
    teaser_id = models.ForeignKey(Idea, related_name='tickers')
    # From        
    # teaser_id = models.IntegerField(null=True, blank=True)

    ticker = models.CharField(max_length=135L, blank=True)
    date_added = models.CharField(max_length=135L, blank=True)
    class Meta:
        db_table = 'teaser_tickers'


class Idea(models.Model):
    id = models.IntegerField(primary_key=True)
    industry_id = models.IntegerField()
    post_type = models.CharField(max_length=45L)

    class Meta:
        db_table = 'idea'

Here are my serializers

class ReverseTickerSerializer(serializers.HyperlinkedModelSerializer):

    class Meta:
        model = myModels.Tickers
        fields = (
            'id'
            ,'ticker'
        )

class IdeaSerializer(serializers.HyperlinkedModelSerializer):
    user = UserSerializer(many=False, read_only=True)
    tickers = ReverseTickerSerializer(many=True, read_only=True)
    teaser = myFields.TeaserField(teaser_length=200, original_field='content')

    class Meta:
        model = myModels.Idea
        fields = (
            'id'
            , 'title'
            , 'date_added'
            , 'user'
            , 'teaser'
            , 'tickers'
        )