About paging query

[wu-clan]

Now I need to use paging query in the joint table, and Use multiple response, What shall I do?

For example:

class Group(models.Model)
    name = models.CharField(max_length=64, verbose_name="group name")

class User(models.Model)
    name = models.CharField(max_length=64, verbose_name="user name")
    group = models.ForeignKey(Group, on_delete=models.CASCADE, verbose_name="by group",
                              related_name='user', related_query_name='user')

class GroupUsers(Schema)
    id: int
    name: str
    group_id: int

@router.get('/groups/{pk}/users', response={404: str, 200: List[GroupUsers]})
@paginate
def get_group_users(request, pk: int)
    group = Group.objects.filter(id=pk).first()
    if not group:
        return 404, "Group does not exist"
    users = Group.objects.filter(user__group=pk).all()
    return users

But this is a failure by 422

[wu-clan]

[mom1]

return 200, users ?

[wu-clan]

@router.get('/groups/{pk}/users', response={200: List[GroupUsers], 404: str})  # put 200 in the front
@paginate
def get_group_users(request, pk: int)
    group = Group.objects.filter(id=pk).first()
    if not group:
        return 404, "Group does not exist"
    users = group.user.all()  # query
    return users

it can work. but, it can only return paginate result, If it's 404, it will trigger schema error by GroupUsers

If remove the paging decorator, it can return to all normally, but I need paging

What shall I do? @vitalik @

[SmileyChris]

This has nothing to do with pagination at all! You're just doing the user query wrong. You want:

users = group.user_set.all()

Removing the pagination decorator definitely does not make things "return to normal".

The key here was to note that your error was 422, with the following error message:

pydantic.error_wrappers.ValidationError: 1 validation error for NinjaResponseSchema
response -> items -> 0 -> group_id
  field required (type=value_error.missing)

Which should get you thinking about why doesn't the item have a group_id. Then you look back at your query and see that you're returning a queryset of groups rather than users, and it all becomes clear.

[wu-clan]

Hi @SmileyChris. I made a complete example to overturn your statement and support my statement

first: because use ForeignKey, therefore, _id will be automatically added to the database field. So use group_id in the Schema Model.

Second, 422 is the initial problem, which is in the changes I propose below new, will not happen 422

third, your query is right, but use related_name='user' in ForeignKey, So group.user.all() is also right

next: This is the complete example and the returned result

# Model
from django.db import models

class Group(models.Model):
    name = models.CharField(max_length=64, verbose_name="group name")


class User(models.Model):
    name = models.CharField(max_length=64, verbose_name="user name")
    group = models.ForeignKey(Group, on_delete=models.CASCADE, verbose_name="by group",
                              related_name='user', related_query_name='user')

# code
from typing import List, Any

from ninja import NinjaAPI, Schema
from ninja.pagination import paginate, PageNumberPagination

from ttt.models import Group, User

router = NinjaAPI(docs_url='/v1/docs')


class Response404(Schema):
    code: int = 404
    msg: str = 'Not Found'
    data: Any = None


class CreateGroup(Schema):
    name: str


class CreateUser(Schema):
    name: str
    group: int


class GroupUsers(Schema):
    id: int
    name: str
    group_id: int


@router.post('/groups')
def create_group(request, group: CreateGroup):
    Group.objects.create(**group.dict())
    return group


@router.post('/users')
def create_user(request, user: CreateUser):
    user.group = Group.objects.filter(id=user.group).first()
    User.objects.create(**user.dict())
    return {'name': user.name}


@router.get('/groups/{pk}/users', response={200: List[GroupUsers], 404: Response404})  # put 200 in the front
@paginate(PageNumberPagination)
def get_group_users(request, pk: int):
    group = Group.objects.filter(id=pk).first()
    if not group:
        return 404, {"msg": "Group does not exist"}
    users = group.user.all()  # query
    return users

# db
group:
-----------
id | name
1  | string
2  | string
-----------

user:
-----------------------
id | name    | group_id
1  | string  | 1
2  | string  | 1
-----------------------

1: group=1
# request
curl -X 'GET' \
  'http://127.0.0.1:8000/groups/1/users?page=1' \
  -H 'accept: application/json'

# response
{
  "items": [
    {
      "id": 1,
      "name": "string",
      "group_id": 1
    },
    {
      "id": 2,
      "name": "string",
      "group_id": 1
    }
  ],
  "count": 2
}

2: group=2
# request
curl -X 'GET' \
  'http://127.0.0.1:8000/groups/2/users?page=1' \
  -H 'accept: application/json'

# response
{
  "items": [],
  "count": 0
}

3: group=3
# request
curl -X 'GET' \
  'http://127.0.0.1:8000/groups/3/users?page=1' \
  -H 'accept: application/json'

# response
Traceback (most recent call last):
  File "C:\ProgramData\Anaconda3\envs\NinjaXia\lib\site-packages\ninja\operation.py", line 100, in run
    return self._result_to_response(request, result)
  File "C:\ProgramData\Anaconda3\envs\NinjaXia\lib\site-packages\ninja\operation.py", line 193, in _result_to_response
    result = response_model.from_orm(resp_object).dict(
  File "C:\ProgramData\Anaconda3\envs\NinjaXia\lib\site-packages\ninja\schema.py", line 161, in from_orm
    return super().from_orm(obj)
  File "pydantic\main.py", line 631, in pydantic.main.BaseModel.from_orm
pydantic.error_wrappers.ValidationError: 6 validation errors for NinjaResponseSchema
response -> items -> 0 -> id
  field required (type=value_error.missing)
response -> items -> 0 -> name
  field required (type=value_error.missing)
response -> items -> 0 -> group_id
  field required (type=value_error.missing)
response -> items -> 1 -> id
  field required (type=value_error.missing)
response -> items -> 1 -> name
  field required (type=value_error.missing)
response -> items -> 1 -> group_id
  field required (type=value_error.missing)

If remove the paging

1: group=1
# request
curl -X 'GET' \
  'http://127.0.0.1:8000/groups/1/users?page=1' \
  -H 'accept: application/json'

# response
[
  {
    "id": 1,
    "name": "string",
    "group_id": 1
  },
  {
    "id": 2,
    "name": "string",
    "group_id": 1
  }
]

2: group=2
# request
curl -X 'GET' \
  'http://127.0.0.1:8000/groups/2/users?page=1' \
  -H 'accept: application/json'

# response
[]

3: group=3
# request
curl -X 'GET' \
  'http://127.0.0.1:8000/groups/3/users?page=1' \
  -H 'accept: application/json'

# response
{
  "code": 404,
  "msg": "Group does not exist",
  "data": null
}

As you can see, the request is normal without the paging

[SmileyChris]

My mistake with my first point. I didn't see that you had made your related_name user (which is just weird, the plural users makes more sense). I usually just use the default _set names and not specify it myself now.

[wu-clan]

[SmileyChris]

Don't keep pinging users like this, it's bad manners.

[wu-clan]

Don't keep pinging users like this, it's bad manners.

I'm sorry for this move

[SmileyChris]

Ah, I see what you're saying now -- it's specifically when you're trying to return a different response type, which you can't do with the paginate decorator. That could definitely do with some better documentation.

What you can do though is raise an exception that ninja will handle. And by default, it handles Django's Http404 error like you want. So all you want is:

from django.shortcuts import get_object_or_404

...

@paginate
def get_group_users(request, pk: int):
    return get_object_or_404(Group, id=pk).user.all()

[wu-clan]

This has given me great inspiration. Thank you very much for your reply