next-with-apollo/src/apollo.ts

Apollo HOC for Next.js

import ApolloClient from 'apollo-client';
// Polyfill fetch
import 'isomorphic-unfetch';
import { InitApolloClient, InitApolloOptions } from './types';

let _apolloClient: ApolloClient<any>;

const ssrMode = !process.browser;

export default function initApollo<TCache = any>(
  clientFn: InitApolloClient<TCache>,
  options?: InitApolloOptions<TCache>
): ApolloClient<TCache> {
  if (!clientFn) {
    throw new Error(
      '[withApollo] the first param is missing and is required to get the ApolloClient'
    );
  }

  if (ssrMode) {
    return getClient<TCache>(clientFn, options);
  }
  if (!_apolloClient) {
    _apolloClient = getClient<TCache>(clientFn, options);
  }

  return _apolloClient;
}

function getClient<TCache>(
  clientFn: InitApolloClient<TCache>,
  options: InitApolloOptions<TCache> = {}
) {
  if (typeof clientFn !== 'function') {
    throw new Error(
      '[withApollo] requires a function that returns an ApolloClient'
    );
  }

  const client = clientFn(options);

  if (options.initialState) client.cache.restore(options.initialState);

  return client;
}