Apollo Server setup in GraphQL - Step-by-Step Execution

Concept Flow - Apollo Server setup

Define typeDefs

↓

Define resolvers

↓

Create ApolloServer instance

↓

Call server.listen()

↓

Server starts and listens

↓

Handle incoming GraphQL requests

The setup starts by defining the schema and resolvers, then creating the server instance, starting it, and finally handling requests.

Execution Sample

GraphQL

const { ApolloServer, gql } = require('apollo-server');

const typeDefs = gql`type Query { hello: String }`;

const resolvers = { Query: { hello: () => 'Hello world!' } };

const server = new ApolloServer({ typeDefs, resolvers });

server.listen().then(({ url }) => console.log(`Server ready at ${url}`));

This code sets up a simple Apollo Server that responds to a 'hello' query with 'Hello world!'.

Execution Table

Step	Action	Evaluation	Result
1	Import ApolloServer and gql	Modules imported	ApolloServer and gql available
2	Define typeDefs with Query type	Schema created	typeDefs holds schema definition
3	Define resolvers for Query.hello	Resolver function created	resolvers object ready
4	Create ApolloServer instance	Server instance created	server object ready
5	Call server.listen()	Server starts listening	Promise resolves with URL
6	Log server URL	Console output	Server ready at http://localhost:4000/
7	Server handles incoming requests	Requests processed	Responds with 'Hello world!' for hello query

💡 Server.listen() promise resolves and server runs indefinitely until stopped

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	After Step 5	Final
typeDefs	undefined	Schema object	Schema object	Schema object	Schema object	Schema object
resolvers	undefined	undefined	Resolver object	Resolver object	Resolver object	Resolver object
server	undefined	undefined	undefined	ApolloServer instance	ApolloServer instance	ApolloServer instance

Key Moments - 3 Insights

Why do we define typeDefs before resolvers?

typeDefs define the schema structure Apollo Server uses; resolvers provide the logic for that schema. The execution_table rows 2 and 3 show typeDefs created first, then resolvers.

What happens when server.listen() is called?

server.listen() starts the server and returns a promise that resolves with the URL. See execution_table row 5 and 6 where the server starts and logs the URL.

How does Apollo Server respond to queries?

Apollo Server uses resolvers to answer queries based on the schema. Row 7 shows the server handling requests and responding with 'Hello world!' for the hello query.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of 'server' after step 4?

A undefined

B ApolloServer instance

C Schema object

D Resolver object

💡 Hint

Check the variable_tracker row for 'server' after step 4

At which step does the server start listening for requests?

A Step 3

B Step 6

C Step 5

D Step 7

💡 Hint

Look at execution_table row describing server.listen()

If we remove the resolvers object, what will happen when a query is made?

A Server will respond with default values or errors

B Server will not start

C Server will crash immediately

D Server will respond with 'Hello world!' anyway

💡 Hint

Resolvers provide response logic; without them, Apollo Server cannot resolve queries properly (see key_moments about resolvers)

Concept Snapshot

Apollo Server setup steps:
1. Define schema with typeDefs using gql.
2. Define resolvers to provide data for schema fields.
3. Create ApolloServer instance with typeDefs and resolvers.
4. Start server with server.listen(), which returns the URL.
5. Server listens and handles GraphQL queries using resolvers.

Full Transcript

To set up Apollo Server, first import ApolloServer and gql. Then define your GraphQL schema using typeDefs. Next, create resolver functions that tell the server how to fetch or compute data for each schema field. After that, create an ApolloServer instance by passing in the typeDefs and resolvers. Call server.listen() to start the server; it returns a promise with the URL where the server is running. Finally, the server listens for incoming GraphQL requests and uses the resolvers to respond. This flow ensures your server understands the schema and knows how to answer queries.