Module 3 Summary

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In Module 3, we've set up a GraphQL API with Apollo Server (in particular with the apollo-express-server package).

src/index.ts

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In the main src/index.ts file, we set up a new Apollo Server instance with the ApolloServer constructor. In the ApolloServer constructor, we pass in a typeDefs string and a resolvers map that we've created in the src/graphql/ folder of our app.

We applied middleware on the Apollo Server instance and passed in the Express app instance as well as specified the path of our API endpoint to be /api.

import express from 'express';
import { ApolloServer } from 'apollo-server-express';
import { typeDefs, resolvers } from './graphql';

const app = express();
const port = 9000;
const server = new ApolloServer({ typeDefs, resolvers });

server.applyMiddleware({ app, path: '/api' });
app.listen(port);

console.log(`[app] : http://localhost:${port}`);

GraphQL Schema

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typeDefs (i.e. type definitions) is a string that represents the GraphQL schema. In the src/graphql/typeDefs.ts file, we use the gql tag that apollo-server-express provides to help parse a template literal into a GraphQL Abstract Tree.

We created a Listing GraphQL object type that represents the shape of a single listing. We also created the root Query and Mutation object types. In the root Query type, we established a listings field where we return a list of listings. The deleteListing field in our Mutation object accepts an id argument and when complete returns the deleted listing.