import { schemaComposer} from 'graphql-compose'; // You may use SDL format for type definition const CityTC = schemaComposer.createObjectTC(`  type City {  code: String!  name: String!  population: Number  countryCode: String  tz: String  } `); // Define type via Config object const CountryTC = schemaComposer.createObjectTC({ name: 'Country', fields: { title: 'String', geo: `type LonLat { lon: Float, lat: Float }`, hoisting: { type: () => AnotherTC, description: `  You may wrap type in thunk for solving  hoisting problems when two types cross reference  each other.  `, } } }); // Or via declarative methods define some additional fields CityTC.addFields({ country: CountryTC, // some another Type ucName: { // standard GraphQL like field definition type: GraphQLString, resolve: (source) => source.name.toUpperCase(), }, currentLocalTime: { // extended GraphQL Compose field definition type: 'Date', resolve: (source) => moment().tz(source.tz).format(), projection: { tz: true }, // load `tz` from database, when requested only `localTime` field }, counter: 'Int', // shortening for only type definition for field complex: `type ComplexType {  subField1: String  subField2: Float  subField3: Boolean  subField4: ID  subField5: JSON  subField6: Date  }`, list0: { type: '[String]', description: 'Array of strings', }, list1: '[String]', list2: ['String'], list3: [new GraphQLOutputType(...)], list4: [`type Complex2Type { f1: Float, f2: Int }`], }); // Add resolver method CityTC.addResolver({ kind: 'query', name: 'findMany', args: { filter: `input CityFilterInput {  code: String!  }`, limit: { type: 'Int', defaultValue: 20, }, skip: 'Int', // ... other args if needed }, type: [CityTC], // array of cities resolve: async ({ args, context }) => { return context.someCityDB .findMany(args.filter) .limit(args.limit) .skip(args.skip); }, }); // Remove `tz` field from schema CityTC.removeField('tz'); // Add description to field CityTC.extendField('name', { description: 'City name', }); schemaComposer.Query.addFields({ cities: CityTC.getResolver('findMany'), currentTime: { type: 'Date', resolve: () => Date.now(), }, }); schemaComposer.Mutation.addFields({ createCity: CityTC.getResolver('createOne'), updateCity: CityTC.getResolver('updateById'), ...adminAccess({ removeCity: CityTC.getResolver('removeById'), }), }); function adminAccess(resolvers) { Object.keys(resolvers).forEach(k => { resolvers[k] = resolvers[k].wrapResolve(next => rp => { // rp = resolveParams = { source, args, context, info } if (!rp.context.isAdmin) { throw new Error('You should be admin, to have access to this action.'); } return next(rp); }); }); return resolvers; } // construct schema which can be passed to express-graphql, apollo-server or graphql-yoga export const schema = schemaComposer.buildSchema();