How to join two models in django-rest-framework

Question

Let say i have two models:

level:

id
file_number
status


level_process:

process_ptr_id
level_id

I want to combine both of my table above to display it in one API using django-rest-framework.. I'm looking for the example on the internet and i cannot find it...by the way i'm using python 2.7 , django 1.10.5 and djangorestframework 3.6.2

serializer.py

class LevelSerializer(serializers.HyperlinkedModelSerializer):
    id = serializers.ReadOnlyField()
    class Meta:
        model = Level
        fields = ('__all__')

class LevelProcessSerializer(serializers.ModelSerializer):
    level = LevelSerializer(read_only=True)

    class Meta:
        model = LevelProcess
        fields = ('__all__')

views.py

class ViewLevelProcessViewSet(viewsets.ModelViewSet):
    processes = LevelProcess.objects.all()
    serializer_class = LevelProcessSerializer(processes, many=True)

Jahongir Rahmonov · Accepted Answer · 2017-04-04T09:35:34.147

22

Try the following. Create serializer for your Level model:

class LevelSerializer(serializers.ModelSerializer):
    class Meta:
        model = Level

Then, inside LevelProcessSerializer, include LevelSerializer like this:

class LevelProcessSerializer(serializers.ModelSerializer):
    level = LevelSerializer(read_only=True)

    class Meta:
        model = LevelProcess

Usage in your ModelViewset:

class ViewLevelProcessViewSet(viewsets.ModelViewSet):
    queryset = LevelProcess.objects.all() 
    serializer_class = LevelProcessSerializer

This way, your json will look something like this:

{
   "id": 1,
   "level": {
      "id": 3,
      "status": "red"
   }
}

Hope this helps!

edited Apr 04 '17 at 09:35

answered Apr 04 '17 at 04:21

Jahongir Rahmonov

13,083
10
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91

@uetoaya this is assuming that `level` inside your `LevelProcess` is a foreign key. If not, let me know – Jahongir Rahmonov Apr 04 '17 at 04:34
yes.. `level_id` is a foreign key in `LevelProcess` – MunirohMansoor Apr 04 '17 at 04:42
what about queryset in my`views?` – MunirohMansoor Apr 04 '17 at 05:00
i try your code and got this error `could not automatically determine the name from the viewset, as it does not have a '.queryset' attribute.` – MunirohMansoor Apr 04 '17 at 05:06
@uetoaya see usage in the answer. The error you got is because of something else, I think. Please, paste your code and I will try to help – Jahongir Rahmonov Apr 04 '17 at 05:26
i change it like this.. `class ViewLevelProcessViewSet(viewsets.ModelViewSet): queryset = LevelProcess.objects.all() serializer_class = LevelProcessSerializer` – MunirohMansoor Apr 04 '17 at 09:27
I'm facing a problem with this. When I try to post data to LevelProcessSerializer's view it does not save level id even though it is sent, Any idea? – Shahabaz Mar 13 '19 at 02:55
what if I want to have a filter on `LevelProcessSerializer` serializer?? – Raju Singh May 20 '20 at 20:14

score 0 · Answer 2 · edited Aug 16 '22 at 09:37

0

class LevelSerializer(serializers.ModelSerializer):
    class Meta:
        model = Level
        fields="__all__"

class LevelProcessSerializer(serializers.ModelSerializer):
    level = LevelSerializer(read_only=True)

class Meta:
    model = LevelProcess
    fields= "__all__"

edited Aug 16 '22 at 09:37

0sVoid

2,547
1
10
25

answered Aug 12 '22 at 10:09

Gyanu Chauhan

1
1

Mohammad Ashraful Islam · Answer 3 · 2017-11-14T06:10:03.133

-3

Don't try to "join" tables. This isn't SQL.

I am assuming your model look like Following,

class Level(models.Model):
    .......

class LevelProcess(models.Model):
    level = models.ForeignKey(Level)

Now, let's walk for query,

l = Level.objects.filter(id=level_id).first()
lp = l.level_process_set.all()

This is how we do in Django ORM.

edited Nov 14 '17 at 06:10

answered Apr 04 '17 at 04:10

Mohammad Ashraful Islam

1,879
15
29

16

Doesn't this result in multiple queries for each related LevelProcess? How is that preferable? It is ultimately SQL, you can't just pretend there's not a database engine behind this thing... – JTW Nov 28 '18 at 19:08

How to join two models in django-rest-framework

3 Answers3

Don't try to "join" tables. This isn't SQL.

Linked

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