graphql-lightning-talk/assets/js/components/Gallery.js

import React from "react";
import gql from "graphql-tag";
import { Query } from "react-apollo";
import Person from "./Person";
import AddFace from "./AddFace";

import LIST_PEOPLE from "../queries/list_people";
import PERSON_ADDED from "../queries/person_added";

class Gallery extends React.Component {
  // Uses Apollo's `subscribeToMore` callback to subscribe to the `personAdded`
  // subscription and update our local data with the new data.
  doSubscription(subscribeToMore) {
    subscribeToMore({
      document: PERSON_ADDED,
      updateQuery: ({ people }, { subscriptionData }) => {
        let newPerson = subscriptionData.data.personAdded;

        let existingPersonIndex = people.findIndex(person => person.username === newPerson.username);
        if (existingPersonIndex >= 0) {
          people.splice(existingPersonIndex, 1, newPerson);
        }
        else {
          people = people.concat([newPerson]);
        }

        return { people };
      }
    });
  }

  render() {
    return (
      <div className="row">
        <Query query={LIST_PEOPLE}>
          {({ subscribeToMore, loading, data }) => {
            if (loading) return null;
            this.doSubscription(subscribeToMore);

            return data.people.map((person, key) => (<Person person={person} key={key} />));
          }}
        </Query>
        <AddFace />
      </div>
    );
  }
}

export default Gallery;