Apollo Server setup in GraphQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is Apollo Server used for?

Apollo Server is a tool that helps you create a GraphQL API easily. It listens for requests and sends back data based on your schema and resolvers.

beginner

Which two main parts do you need to define when setting up Apollo Server?

You need to define the type definitions (schema) and the resolvers (functions that fetch data).

beginner

What is the purpose of the typeDefs in Apollo Server?

typeDefs define the shape of your data and the queries or mutations clients can make. Think of it as a contract between client and server.

beginner

How do you start Apollo Server to listen for requests?

You call the listen() method on the Apollo Server instance. It starts the server and waits for client requests.

beginner

What is a resolver in Apollo Server?

A resolver is a function that tells Apollo Server how to get the data for a specific field in your schema. It connects the schema to your data sources.

What do you need to provide to Apollo Server to define your API's data structure?

A typeDefs

B Resolvers

C Middleware

D Database connection

typeDefs define the data structure and queries in Apollo Server.

Which method starts the Apollo Server to listen for incoming requests?

A listen()

B start()

C run()

D execute()

The listen() method starts the server and waits for requests.

What role do resolvers play in Apollo Server?

A Define the schema

B Fetch data for schema fields

C Handle server errors

D Manage user authentication

Resolvers fetch or compute the data for each field in the schema.

Which of the following is NOT required to set up a basic Apollo Server?

A typeDefs

B Resolvers

C Database connection

D Server listen method

A database connection is optional; Apollo Server can serve static data or other sources.

Apollo Server is primarily used to build what kind of API?

A File API

B REST API

C SOAP API

D GraphQL API

Apollo Server is designed to build GraphQL APIs.

Explain the basic steps to set up Apollo Server from scratch.

Think about what you need to tell Apollo Server about your data and how to start it.

Describe the roles of typeDefs and resolvers in Apollo Server.

One defines the shape, the other provides the content.

Practice

1. What is the main purpose of Apollo Server in a GraphQL application?

easy

A. To manage user authentication only

B. To style the frontend user interface

C. To store data in a database

D. To create and run a GraphQL API server

Solution

1. Step 1: Understand Apollo Server's role

   Apollo Server is designed to create and run GraphQL APIs, handling client requests and responses.

2. Step 2: Differentiate from other roles

   Styling UI, storing data, or managing authentication are separate concerns not handled by Apollo Server itself.

3. Final Answer:

   To create and run a GraphQL API server -> Option D

4. Quick Check:

   Apollo Server = GraphQL API server [OK]

Hint: Apollo Server runs GraphQL APIs, not UI or database [OK]

Common Mistakes:

• Confusing Apollo Server with frontend tools
• Thinking Apollo Server stores data
• Assuming Apollo Server only handles authentication

2. Which of the following is the correct way to import ApolloServer from the Apollo Server package in a Node.js project?

easy

A. import ApolloServer from 'apollo-server';

B. const ApolloServer = require('apollo-server');

C. const { ApolloServer } = require('apollo-server');

D. import { ApolloServer } from 'apollo-server';

Solution

1. Step 1: Identify correct CommonJS import syntax

   In Node.js using CommonJS, destructuring import is done with const { ApolloServer } = require('apollo-server');.

2. Step 2: Check other options

   import { ApolloServer } from 'apollo-server'; is ES module syntax, const ApolloServer = require('apollo-server'); incorrectly assigns the entire module, import ApolloServer from 'apollo-server'; misses destructuring.

3. Final Answer:

   const { ApolloServer } = require('apollo-server'); -> Option C

4. Quick Check:

   CommonJS import with destructuring = const { ApolloServer } = require('apollo-server'); [OK]

Hint: Use destructuring with require for ApolloServer in Node.js [OK]

Common Mistakes:

• Using ES module import in CommonJS environment
• Not destructuring ApolloServer from the package
• Assigning require result directly without destructuring

3. Given the following Apollo Server setup code, what will be the output when querying { hello }?

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

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

const resolvers = { Query: { hello: () => 'Hi there!' } };

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

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

medium

A. SyntaxError: Missing resolver for 'hello'

B. { "data": { "hello": "Hi there!" } }

C. { "data": { "hello": "Hello World" } }

D. Server fails to start due to missing typeDefs

Solution

1. Step 1: Analyze typeDefs and resolvers

   The schema defines a Query type with a 'hello' field returning String. The resolver returns 'Hi there!'.

2. Step 2: Predict query response

   Querying { hello } returns the resolver's string 'Hi there!' wrapped in data JSON.

3. Final Answer:

   { "data": { "hello": "Hi there!" } } -> Option B

4. Quick Check:

   Query { hello } = 'Hi there!' response [OK]

Hint: Resolver return value matches query response [OK]

Common Mistakes:

• Assuming default 'Hello World' response
• Thinking missing resolver causes syntax error
• Confusing server start errors with query output

4. Identify the error in this Apollo Server setup code snippet:

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

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

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

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

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

medium

A. The resolver field name 'greet' does not match the schema field 'greeting'

B. Missing import of ApolloServer

C. Syntax error in typeDefs definition

D. Server.listen() is missing a callback function

Solution

1. Step 1: Compare schema and resolver fields

   The schema defines a Query field named 'greeting', but the resolver defines 'greet'. They must match exactly.

2. Step 2: Understand impact of mismatch

   This mismatch causes the 'greeting' field to have no resolver, resulting in null or error responses.

3. Final Answer:

   The resolver field name 'greet' does not match the schema field 'greeting' -> Option A

4. Quick Check:

   Schema and resolver field names must match [OK]

Hint: Schema and resolver field names must be identical [OK]

Common Mistakes:

• Assuming resolver names can differ from schema
• Ignoring case sensitivity in field names
• Thinking server.listen() needs a callback argument

5. You want to extend your Apollo Server to fetch user data from a database. Which setup correctly integrates a data source into Apollo Server?

hard

A. Pass a dataSources function returning an object with your database API instance to ApolloServer constructor

B. Add database queries directly inside typeDefs

C. Define database connection inside gql template literal

D. Call database queries inside server.listen() callback

Solution

1. Step 1: Understand Apollo Server dataSources option

   Apollo Server accepts a dataSources function that returns objects to access external data, like databases.

2. Step 2: Evaluate other options

   Database queries do not belong in typeDefs or gql strings, and server.listen() is for starting the server, not querying data.

3. Final Answer:

   Pass a dataSources function returning an object with your database API instance to ApolloServer constructor -> Option A

4. Quick Check:

   Use dataSources to connect databases in Apollo Server [OK]

Hint: Use dataSources function to add databases to Apollo Server [OK]

Common Mistakes:

• Putting queries inside schema definitions
• Trying to query database in server.listen callback
• Ignoring Apollo Server's dataSources feature