Django & Graphene：如何处理多态模型的双向关系？

Question

我有一个看起来像这样的 Django 模型（当然是简化的）：

from django.db import models
from polymorphic.models import PolymorphicModel

class Tournament(models.Model):
    slug = models.CharField(max_length=100, unique=True)

class Event(PolymorphicModel):
    tournament = models.ForeignKey(Tournament, related_name='events')
    slug = models.CharField(max_length=100)

class PracticeEvent(Event):
    pass

class MatchEvent(Event):
    winner = models.CharField(max_length=100, null=True, blank=True, default=None)

锦标赛包括两种赛事：练习赛和比赛。我想使用 GraphQL 和 Graphene 公开这个模型。这是我想出的：

import graphene
from graphene_django import DjangoObjectType

from . import models

class TournamentType(DjangoObjectType):
    class Meta:
        model = models.Tournament
        exclude_fields = ('id',)

class EventType(graphene.Interface):
    tournament = graphene.Field(TournamentType, required=True)
    slug = graphene.String(required=True)

class PracticeEventType(DjangoObjectType):
    class Meta:
        model = models.PracticeEvent
        interfaces = (EventType,)
        exclude_fields = ('id',)

class MatchEventType(DjangoObjectType):
    class Meta:
        model = models.MatchEvent
        interfaces = (EventType,)
        exclude_fields = ('id',)

extra_types = {PracticeEventType, MatchEventType}

class Query(graphene.ObjectType):
    tournaments = graphene.List(TournamentType)
    events = graphene.List(EventType)
    # ... resolvers ...

schema = graphene.Schema(
    query=Query,
    types=schema_joust.extra_types,)

到现在为止还挺好; 我可以events { ... }直接查询，甚至tournament可用。但是，由于没有DjangoObjectTypewith model = models.Event，我无法查询tournaments { events {...} }...

我怎样才能解决这个问题？我不能做EventType一个DjangoObjectTpe，我不知道添加events的事实后场。

Answer 1

靠他们自己，EventType.tournament并TournamentType.events没有那么难。第一个显示在问题中，第二个可以这样实现：

class EventType(graphene.Interface):
    slug = graphene.String(required=True)

class TournamentType(DjangoObjectType):
    class Meta:
        model = models.Tournament
        exclude_fields = ('id',)

    events = graphene.List(EventType)

    def resolve_events(self, info):
        return self.events.all()

graphene-django 无法识别这种关系，但是手动声明和解析该字段可以解决问题。为了获得反向场，如果我们不需要引用TournamentType，这将起作用，我深入研究了 graphene-django 并找到了graphene_django.converter.convert_django_field_with_choices. 这让我们可以这样定义字段：

import graphene
from graphene_django import DjangoObjectType, converter, registry

from . import models

class EventType(graphene.Interface):
    tournament = converter.convert_django_field_with_choices(
        models.Event.tournament.field, registry.get_global_registry())
    slug = graphene.String(required=True)