graphene_connection_union.py

import graphene
from graphene import relay

from graphene.core.classtypes import UnionType


schema = graphene.Schema(name='Starwars Relay Schema')


class Adjective(relay.Node):
    '''An adjective'''
    string = graphene.String(description='The adjective string')

    def get_node(self, args, info):
        pass


class Verb(relay.Node):
    '''A verb'''
    string = graphene.String(description='The verb string')

    def get_node(self, args, info):
        pass


class AdjectiveOrVerb(UnionType):
    class Meta:
        types = [Adjective, Verb]


class GenericWord(relay.Node):
    word = graphene.Field(AdjectiveOrVerb)

    def get_node(self, args, info):
        pass


class Query(graphene.ObjectType):
    # Using a UnionType is not supported by the Relay spec
    # as it requires a ObjectType
    # https://github.com/graphql/graphql-relay-js/issues/41
    # so we will use a GenericWord wrapper around it
    # things_to_learn = relay.ConnectionField(AdjectiveOrVerb)
    things_to_learn = relay.ConnectionField(GenericWord)
    node = relay.NodeField()

    def resolve_things_to_learn(self, args, info):
        return [GenericWord(word=Adjective(string='warm')), GenericWord(word=Verb(string='look'))]


schema.query = Query


def test_query():
    query = '''
    query {
      thingsToLearn {
        edges {
          node {
            word {
              ... on Adjective {
                string
              }
              ... on Verb {
                string
              }
            }
          }
        }
      }
    }
    '''
    expected = {
        'thingsToLearn': {
            'edges': [
                {
                    'node': {
                        'word': {
                            'string': 'warm'
                        }
                    }
                },
                {
                    'node': {
                        'word': {
                            'string': 'look'
                        }
                    }
                }
            ]
        }
    }
    result = schema.execute(query)
    assert not result.errors
    assert result.data == expected
    print result.data

if __name__ == '__main__':
    test_query()