Type & Field Policy API example

typePolicy.ts

export const cache = new InMemoryCache({
  ...possibleTypes,
  typePolicies: {
    Query: {
      fields: {
        card(existingData, { args, toReference }) {
          return (
            existingData || toReference({ __typename: 'Card', id: args?.id })
          );
        },
        category(existingData, { args, toReference }) {
          return (
            existingData ||
            toReference({ __typename: 'Category', id: args?.id })
          );
        },
      },
    },
    Card: {
      fields: {
        categories: {
          keyArgs: [],
        },
      },
    },
    Category: {
      fields: {
        cards: {
          keyArgs: [],
          merge(existing, incoming, { args }) {
            return incoming; // this example is just returning the incoming
          },
        },
      },
    },
  },
});