[GraphQL] Use GraphQLNonNull for Required Fields

While certain fields in a GraphQL Schema can be optional, there are some fields or arguments that are necessary in order to either fulfill a query, or to provide a guarantee to people using the Schema that some field exists. In this video, we'll take a look at turning an argument in a NonNull argument by applying the GraphQLNonNull type in order to guarantee that the given argument is supplied in the query.

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

const {
GraphQLSchema,
GraphQLObjectType,
GraphQLString,
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 queryType = new GraphQLObjectType({
name: 'QueryType',
description: 'The root query type',
fields :{
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
});

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

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

If gave the query:

{
video{
id
title
duration
watched
}
}

Then will get the result as:

{
"errors": [
{
"message": "Field \"video\" argument \"id\" of type \"ID!\" is required but not provided.",
"locations": [
{
"line": 2,
"column": 3
}
]
}
]
}

Then if get id args will get result as normal:

{
video (id:"a"){
id
title
duration
watched
}
}