django rest framework lookup_field through OneToOneField

Question

https://gist.github.com/ranman/3d97ea9054c984bca75e

Desired Behavior
User lookup happens by the username: /api/users/randall
Speaker lookup happens by the username as well: /api/speakers/randall

Constraints
Not all users are speakers. All speakers are users.

models.py

from django.contrib.auth.models import User

class Speaker(models.Model):
    user = models.OneToOneField(User)

serializers.py

class UserSerializer(serializers.HyperlinkedModelSerializer):
    class Meta:
        model = User
        fields = ('url', 'username', 'email', 'groups')
        lookup_field = 'username'
 
class SpeakerSerializer(serializers.HyperlinkedModelSerializer):
    user = serializers.HyperlinkedRelatedField(
        view_name='user-detail',
        read_only=True,
        lookup_field='username'
    )
    class Meta:
        model = Speaker
        lookup_field = 'user'

views.py

class UserViewSet(viewsets.ModelViewSet):
    queryset = User.objects.all()
    serializer_class = UserSerializer
    lookup_field = 'username'
    
class SpeakerViewSet(viewsets.ModelViewSet):
    queryset = Speaker.objects.all().select_related('user')
    serializer_class = SpeakerSerializer
    lookup_field = "user"

I've tried various different invocations of lookup_field and serializer types to get this working to no avail. It may not be possible without a lot more code. I'm just wondering what direction I can take.

Solution

This is how I managed to hack it

models.py

from django.db import models    
from django.contrib.auth.models import User

class Speaker(models.Model):
    user = models.OneToOneField(User)

    @property
    def user__username(self):
        return self.user.username
    
    def __unicode__(self):
        return self.user.username

serializers.py

from .models import Speaker
from rest_framework import serializers
from django.contrib.auth.models import User

class UserSerializer(serializers.HyperlinkedModelSerializer):
    class Meta:
        model = User
        fields = ('url', 'username', 'email', 'groups')
        lookup_field = 'username'

class SpeakerSerializer(serializers.HyperlinkedModelSerializer):
    user = serializers.HyperlinkedRelatedField(
        view_name='user-detail',
        read_only=True,
        lookup_field='username'
    )
    class Meta:
        model = Speaker
        fields = ('url', 'user')
        lookup_field = 'user__username'

view.py

from .models import Speaker
from .serializers import SpeakerSerializer, UserSerializer

from rest_framework import viewsets
from django.contrib.auth.models import User

class UserViewSet(viewsets.ModelViewSet):
    queryset = User.objects.all()
    serializer_class = UserSerializer
    lookup_field = 'username'

class SpeakerViewSet(viewsets.ModelViewSet):
    queryset = Speaker.objects.all().select_related('user')
    serializer_class = SpeakerSerializer
    lookup_field = 'user__username'

Comments

[Kevin Brown-Silva]

Have you tried using double underscores in the lookup_field to see if that can work? It'd be similar to a queryset filter.

[Randall Hunt]

I've tried using lookup_field = "user__username" and it doesn't work. I've tried using that on both the model and the view to no avail :( 'Speaker' object has no attribute 'user__username'

[levi]

@ranman what do you want ? do you want to serialize a related object ?

[Randall Hunt]

I want to be able to lookup the speaker object by the username on the user associated with the speaker

[Randall Hunt]

'Speaker' object has no attribute 'user__username' doesn't seem to work. I might have implemented it incorrectly.

[Randall Hunt]

Actually it doesn't work -- for some reason this doesn't allow 2 things: the user field is no longer able to be written to when you create a new speaker, the speaker is no longer renderable on items that have relations to it

[Todor]

How can i reproduce your errors? I mean I tried to create a new speaker via the python shell and it pass with no problems, if you try to create a speaker via the api, well the user field is marked as read-only, that's why it doesn't work. I also created a dummy model having OneToOneField to the speaker, this also worked with both ModelSerializer and HyperlinkedModelSerializer with the 2nd one i just had to redefine the speaker field with as HyperlinkedRelatedField with lookup_field='user__username'(the same thing was done in the SpeakerSerializer for the user field.