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43 lines
1.3 KiB
Python
43 lines
1.3 KiB
Python
from .unmountedtype import UnmountedType
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from .objecttype import ObjectType
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from .base import BaseOptions, BaseType
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class UnionOptions(BaseOptions):
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types = () # type: List[Type[ObjectType]]
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class Union(UnmountedType, BaseType):
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'''
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Union Type Definition
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When a field can return one of a heterogeneous set of types, a Union type
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is used to describe what types are possible as well as providing a function
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to determine which type is actually used when the field is resolved.
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'''
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@classmethod
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def __init_subclass_with_meta__(cls, types=None, **options):
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assert (
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isinstance(types, (list, tuple)) and
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len(types) > 0
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), 'Must provide types for Union {name}.'.format(name=cls.__name__)
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_meta = UnionOptions(cls)
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_meta.types = types
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super(Union, cls).__init_subclass_with_meta__(_meta=_meta, **options)
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@classmethod
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def get_type(cls):
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'''
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This function is called when the unmounted type (Union instance)
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is mounted (as a Field, InputField or Argument)
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'''
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return cls
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@classmethod
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def resolve_type(cls, instance, context, info):
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from .objecttype import ObjectType
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if isinstance(instance, ObjectType):
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return type(instance)
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