PROTOCOL

RootSelectionSet

1public protocol RootSelectionSet: AnySelectionSet, OutputTypeConvertible

A selection set that represents the root selections on its __parentType. Nested selection sets for type cases are not RootSelectionSets.

While a TypeCase only provides the additional selections that should be selected for its specific type, a RootSelectionSet guarantees that all fields for itself and its nested type cases are selected.

When considering a specific TypeCase, all fields will be selected either by the root selection set, a fragment spread, the type case itself, or another compatible TypeCase on the root selection set.

This is why only a RootSelectionSet can be executed by a GraphQLExecutor. Executing a non-root selection set would result in fields from the root selection set not being collected into the ResponseDict for the SelectionSet's data.