examplePlugin.ts

const { makeExtendSchemaPlugin, gql } = require("graphile-utils");
const { convertUsdToAud } = require("ficticious-npm-library");

const MyForeignExchangePlugin = makeExtendSchemaPlugin(build => {
  return {
    typeDefs: gql`
      extend type Product {
        priceInAuCents: Int!
          @requires(columns: ["price_in_us_cents"])
      }
    `,
    resolvers: {
      Product: {
        priceInAuCents: async product => {
          const { priceInUsCents } = product;
          return await convertUsdToAud(priceInUsCents);
        },
      },
    },
  };
});