Apollo Client - 2.5.0 - Resolver

apollo-client-250-resolver.js

const client = new ApolloClient({
  cache: new InMemoryCache(),
  link: new HttpLink({
    uri: 'http://localhost:4000/graphql',
  }),
  resolvers: {
    Launch: {
      isInCart: (launch, _args, { cache }) => {
        const { cartItems } = cache.readQuery({ 
          query: GET_CART_ITEMS 
        });
        return cartItems.includes(launch.id);
      },
    },
  },
});