Apollo Client

Union Types

When using an union type with the GraphQL Code Generator, it’s possible to infer the type by including __typename in the query, then in the code running some kind of conditional expression (like an if statement or switch cases) to filter the event type via the __typename property. That will it will infer the type of the union.

Normalized Object Types

When using a normalized object type that shares the primary key field with other objects (therefore its not unique by itself), you need to add a Type Policy to uniquely identify the data. Otherwise, the local cache will get overridden with new data, because the Apollo Client, will by default, treat id or _id as the primary key.