[GraphQL] Write a GraphQL Mutation

In order to change the data that we can query for in a GraphQL Schema, we have to define what is called a mutation in GraphQL. Mutations allow us to specify ways to create, update, and delete data. It also provides a way to fetch information after the mutation occurs. In this video, we’ll learn how to create a Mutation Type in GraphQL and specify the information we want returned.

const express                                  = require('express');
const graphqlHttp                              = require('express-graphql');
const {
    getVideoById, getVideos, createVideo } = require('./data/index');
const server                                   = express();
const port                                     = process.env.PORT || 3000;

const {
          GraphQLSchema, GraphQLObjectType, GraphQLString, GraphQLList, GraphQLInt, GraphQLNonNull, GraphQLBoolean, GraphQLID
      } = require('graphql');

const videoType = new GraphQLObjectType({
    name        : 'video',
    description : 'A video on Egghead.io',
    fields      : {
        id       : {
            type        : GraphQLID,
            description : 'The id of the video'
        },
        title    : {
            type        : GraphQLString,
            description : 'The title of the video'
        },
        duration : {
            type        : GraphQLInt,
            description : 'The duration of the video'
        },
        watched  : {
            type        : GraphQLBoolean,
            description : 'Whether or no the viewer watched the video'
        }
    }
});

const mutationType = new GraphQLObjectType({
                                           name        : 'Mutation',
                                           description : 'The root Mutation type',
                                           fields      : {
                                               createVideo : {
                                                   type    : videoType,
                                                   args    : {
                                                       title    : {
                                                           type        : new GraphQLNonNull(GraphQLID),
                                                           description : 'The title of the video'
                                                       },
                                                       duration : {
                                                           type        : new GraphQLNonNull(GraphQLInt),
                                                           description : 'The duration of the video'
                                                       },
                                                       watched  : {
                                                           type : new GraphQLNonNull(GraphQLBoolean)
                                                       }
                                                   },
                                                   resolve : (_, args) => {
                                                       return createVideo(args)
                                                   }
                                               }
                                           }
                                       });

const queryType = new GraphQLObjectType({
    name        : 'QueryType',
    description : 'The root query type',
    fields      : {
        videos : {
            type    : new GraphQLList(videoType),
            resolve : getVideos
        },
        video  : {
            type    : videoType,
            args    : {
                id : {
                    type        : new GraphQLNonNull(GraphQLID),
                    description : 'The id of the video'
                }
            },
            resolve : (_, args) => getVideoById(args.id)
        }
    }
});

const schema = new GraphQLSchema({
    query    : queryType,
    mutation : mutationType
});

server.use('/graphql', graphqlHttp({
                                       schema,
                                       graphiql : true, // use graphiql interface
                                   }));

server.listen(port, () => {
    console.log(`Listening on http`)
})

Write mutation in GraphiQL:

mutation video {
  createVideo(title: "new Redux", duration:450, watched: false) {
    id,
    title
  }
}

Data:

const videoA = {
    id: 'a',
    title: 'Create a GraphQL Schema',
    duration: 120,
    released: true,
};
const videoB = {
    id: 'b',
    title: 'Ember.js CLI',
    duration: 240,
    released: false,
};
const videos = [videoA, videoB];
const getVideoById = (id) => new Promise((resolve) => {
    const [video] = videos.filter((video) => {
        return video.id === id;
    });

    resolve(video);
});
const getVideos = () => new Promise((resolve) => resolve(videos));
const createVideo = ({ title, duration, released }) => {
    const video = {
        id: (new Buffer(title, 'utf8')).toString('base64'),
        title,
        duration,
        released,
    };

    videos.push(video);

    return video;
};

exports.getVideoById = getVideoById;
exports.getVideos = getVideos;
exports.createVideo = createVideo;