Source code for graphene.types.union

from .base import BaseOptions, BaseType
from .unmountedtype import UnmountedType

# For static type checking with Mypy
MYPY = False
if MYPY:
    from .objecttype import ObjectType  # NOQA
    from typing import Iterable, Type  # NOQA

class UnionOptions(BaseOptions):
    types = ()  # type: Iterable[Type[ObjectType]]

[docs]class Union(UnmountedType, BaseType): """ Union Type Definition When a field can return one of a heterogeneous set of types, a Union type is used to describe what types are possible as well as providing a function to determine which type is actually used when the field is resolved. The schema in this example can take a search text and return any of the GraphQL object types indicated: Human, Droid or Starship. Ambiguous return types can be resolved on each ObjectType through ``Meta.possible_types`` attribute or ``is_type_of`` method. Or by implementing ``resolve_type`` class method on the Union. .. code:: python from graphene import Union, ObjectType, List class SearchResult(Union): class Meta: types = (Human, Droid, Starship) class Query(ObjectType): search = List(SearchResult.Field( search_text=String(description='Value to search for')) ) Meta: types (Iterable[graphene.ObjectType]): Required. Collection of types that may be returned by this Union for the graphQL schema. name (optional, str): the name of the GraphQL type (must be unique in schema). Defaults to class name. description (optional, str): the description of the GraphQL type in the schema. Defaults to class docstring. """ @classmethod def __init_subclass_with_meta__(cls, types=None, **options): assert ( isinstance(types, (list, tuple)) and len(types) > 0 ), f"Must provide types for Union {cls.__name__}." _meta = UnionOptions(cls) _meta.types = types super(Union, cls).__init_subclass_with_meta__(_meta=_meta, **options) @classmethod def get_type(cls): """ This function is called when the unmounted type (Union instance) is mounted (as a Field, InputField or Argument) """ return cls @classmethod def resolve_type(cls, instance, info): from .objecttype import ObjectType # NOQA if isinstance(instance, ObjectType): return type(instance)