Differences with mesosphere/reactive-graphql

PR#19 merged: Fix resolvers returning undefined
PR#23 merged: Fix error thrown for nullable field resolving null
PR#25 merged: Fix tests that are skiped

Reactive GraphQL

GraphQL reactive executor

Execute GraphQL queries against reactive resolvers (resolvers that return Observable) to get a reactive results.

This project aims to become a complete GraphQL implementation based around RxJS.

Install

$ npm i reactive-graphql --save

Usage

The usage is very similar to graphql-js's graphql function, except that:

resolvers can return an Observable
the returned value is an Observable

import { makeExecutableSchema } from "graphql-tools";
import gql from "graphql-tag";
import { timer } from "rxjs";
import graphql from "reactive-graphql";

const typeDefs = `
  type Query {
    time: Int!
  }
`;

const resolvers = {
  Query: {
    // resolvers can return an Observable
    time: () => {
      // Observable that emits increasing numbers every 1 second
      return timer(1000, 1000);
    }
  }
};

const schema = makeExecutableSchema({
  typeDefs,
  resolvers
});

const query = gql`
  query {
    time
  }
`;

const stream = graphql(query, schema);
// stream is an Observable
stream.subscribe(res => console.log(res));

outputs

{ data: { time: 0 } }
{ data: { time: 1 } }
{ data: { time: 2 } }
{ data: { time: 3 } }
{ data: { time: 4 } }
...

API

The first argument you pass into reactive-graphql is a GraphQL query, either parsed or as string, the second one is an executable schema. You can pass in the root context as an object as a third parameter. The variables can be passed as 4th parameter.

The implementation will always return an Observable. If any of the resolvers returns an error the implementation will emit the error on the stream. Otherwise the data will be wrapped in a { data } object, like most implementations handle this.

Caveats

Unsupported GraphQL features:

fragments of all kinds
subscriptions (as everything is treated as a subscription)

Advanced usage

import React from "react";
import ReactDOM from "react-dom";
import "./styles.css";

import { graphql } from "reactive-graphql";

import { makeExecutableSchema } from "graphql-tools";
import { from, interval, of } from "rxjs";
import { map, merge, scan, combineLatest } from "rxjs/operators";
import { componentFromStream } from "@dcos/data-service";

// mocked API clients that return Observables
const oldPosts = from(["my first post", "a second post"]);
const newPosts = interval(3000).pipe(map(v => `Blog Post #${v + 1}`));
const fetchPosts = () =>
  oldPosts.pipe(
    merge(newPosts),
    scan((acc, item) => [...acc, item], [])
  );
const votesStore = {};
const fetchVotesForPost = name => of(votesStore[name] || 0);

const schema = makeExecutableSchema({
  typeDefs: `
  type Post {
    id: Int!
    title: String!
    votes: Int!
  }

  # the schema allows the following query:
  type Query {
    posts: [Post]
  }

  # this schema allows the following mutation:
  type Mutation {
    upvotePost (
      postId: Int!
    ): Post
  }
  `,
  resolvers: {
    Query: {
      posts(parent, args, context) {
        return fetchPosts().pipe(
          map(emittedValue =>
            emittedValue.map((value, index) => ({ id: index, title: value }))
          )
        );
      }
    },
    Post: {
      votes(parent, args, context) {
        return fetchVotesForPost(parent.title);
      }
    }
  }
});

const query = `
  query {
    posts {
      title
      votes
    }
  }
`;

const postStream = graphql(schema, query);
const PostsList = componentFromStream(propsStream =>
  propsStream.pipe(
    combineLatest(postStream, (props, result) => {
      const {
        data: { posts }
      } = result;

      return posts.map(post => (
        <div>
          <h3>{post.title}</h3>
        </div>
      ));
    })
  )
);

function App() {
  return (
    <div className="App">
      <PostsList />
    </div>
  );
}

const rootElement = document.getElementById("root");
ReactDOM.render(<App />, rootElement);

License

Apache 2.0

getstation / reactive-graphql