Apollo Client setup in GraphQL - Mini Project: Build & Apply

Apollo Client Setup

📖 Scenario: You are building a simple web app that fetches data from a GraphQL server. To do this, you need to set up Apollo Client, which helps your app talk to the GraphQL server easily.

🎯 Goal: Set up Apollo Client step-by-step to connect your app to a GraphQL endpoint and prepare it to fetch data.

📋 What You'll Learn

Create an Apollo Client instance with the correct URI

Set up an in-memory cache for Apollo Client

Configure Apollo Client with the cache and URI

Export the Apollo Client instance for use in the app

💡 Why This Matters

🌍 Real World

Apollo Client is widely used in web apps to connect to GraphQL servers, making data fetching easier and more efficient.

💼 Career

Knowing how to set up Apollo Client is essential for frontend developers working with GraphQL APIs in modern web development.

1

Import ApolloClient and InMemoryCache

Write the import statements to bring in ApolloClient and InMemoryCache from the @apollo/client package.

GraphQL

// Import ApolloClient and InMemoryCache from '@apollo/client'
// Your code here

Hint

Use ES6 import syntax to import both ApolloClient and InMemoryCache from the @apollo/client package.

2

Create the Apollo Client URI variable

Create a constant variable called GRAPHQL_URI and set it to the string 'https://example.com/graphql' which is the GraphQL server endpoint.

GraphQL

import { ApolloClient, InMemoryCache } from '@apollo/client';

// Create a constant GRAPHQL_URI with the value 'https://example.com/graphql'
// Your code here

Hint

Use const to create a variable named GRAPHQL_URI and assign the exact URL string.

3

Initialize Apollo Client with URI and cache

Create a constant called client and assign it a new ApolloClient instance. Pass an object with two properties: uri set to GRAPHQL_URI and cache set to a new InMemoryCache().

GraphQL

import { ApolloClient, InMemoryCache } from '@apollo/client';

const GRAPHQL_URI = 'https://example.com/graphql';

// Create Apollo Client instance named client with uri and cache
// Your code here

Hint

Use the new keyword to create an ApolloClient object with the correct uri and cache properties.

4

Export the Apollo Client instance

Add a line to export the client constant as the default export of the module.

GraphQL

import { ApolloClient, InMemoryCache } from '@apollo/client';

const GRAPHQL_URI = 'https://example.com/graphql';

const client = new ApolloClient({
  uri: GRAPHQL_URI,
  cache: new InMemoryCache()
});

// Export the client as default
// Your code here

Hint

Use export default client; to make the Apollo Client instance available to other parts of your app.

Practice

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

easy

A. To connect your app to a GraphQL server and manage data

B. To create a new GraphQL server

C. To style your app's user interface

D. To store data permanently on the server

Solution

1. Step 1: Understand Apollo Client's role

   Apollo Client is designed to connect your app to a GraphQL server and handle data fetching and caching.

2. Step 2: Differentiate from other roles

   Creating servers or styling UI are not responsibilities of Apollo Client.

3. Final Answer:

   To connect your app to a GraphQL server and manage data -> Option A

4. Quick Check:

   Apollo Client = Connect and manage data [OK]

Hint: Apollo Client connects app to server and manages data [OK]

Common Mistakes:

• Confusing Apollo Client with server creation tools
• Thinking Apollo Client styles the UI
• Assuming Apollo Client stores data permanently on server

2. Which of the following is the correct way to create an Apollo Client instance with a server URL 'https://api.example.com/graphql'?

easy

A. const client = new ApolloClient({ endpoint: 'https://api.example.com/graphql' });

B. const client = ApolloClient({ url: 'https://api.example.com/graphql', cache: new Cache() });

C. const client = new ApolloClient({ uri: 'https://api.example.com/graphql', cache: new InMemoryCache() });

D. const client = new ApolloClient('https://api.example.com/graphql');

Solution

1. Step 1: Check Apollo Client constructor syntax

   The correct syntax uses 'new ApolloClient' with an object containing 'uri' and 'cache' properties.

2. Step 2: Verify property names and cache setup

   The property for the server URL is 'uri', and the cache should be an instance of 'InMemoryCache'.

3. Final Answer:

   const client = new ApolloClient({ uri: 'https://api.example.com/graphql', cache: new InMemoryCache() }); -> Option C

4. Quick Check:

   Use 'uri' and 'InMemoryCache' in ApolloClient setup [OK]

Hint: Use 'uri' and 'new InMemoryCache()' when creating Apollo Client [OK]

Common Mistakes:

• Using 'url' or 'endpoint' instead of 'uri'
• Not using 'new' keyword with ApolloClient
• Omitting the cache property or using wrong cache class

3. Given this Apollo Client setup code, what will console.log(client.cache.extract()) output immediately after creation?

const client = new ApolloClient({
  uri: 'https://api.example.com/graphql',
  cache: new InMemoryCache()
});
console.log(client.cache.extract());

medium

A. A string with the server URL

B. null

C. An error because cache is not initialized

D. {} (an empty object)

Solution

1. Step 1: Understand InMemoryCache initial state

   When a new InMemoryCache is created, it starts empty with no stored data.

2. Step 2: Check what extract() returns

   The extract() method returns the current cache contents as an object. Since no queries ran yet, it returns an empty object {}.

3. Final Answer:

   {} (an empty object) -> Option D

4. Quick Check:

   New cache extract() = empty object {} [OK]

Hint: New cache is empty; extract() returns {} [OK]

Common Mistakes:

• Expecting data before any query runs
• Thinking extract() returns null or error
• Confusing cache contents with server URL

4. Identify the error in this Apollo Client setup code:

const client = new ApolloClient({
  url: 'https://api.example.com/graphql',
  cache: new InMemoryCache()
});

medium

A. Missing 'new' keyword before InMemoryCache

B. Property 'url' should be 'uri'

C. ApolloClient should not be called with 'new'

D. Cache property should be a string, not an object

Solution

1. Step 1: Check property names in Apollo Client config

   The correct property for the server address is 'uri', not 'url'.

2. Step 2: Verify cache instantiation

   The cache is properly instantiated as new InMemoryCache(). The primary error is the incorrect property name.

3. Final Answer:

   Property 'url' should be 'uri' -> Option B

4. Quick Check:

   Use 'uri' property for server URL [OK]

Hint: Use 'uri' not 'url' for server address in Apollo Client [OK]

Common Mistakes:

• Using 'url' instead of 'uri'
• Forgetting 'new' before InMemoryCache()
• Thinking ApolloClient is called without 'new'

5. You want to set up Apollo Client to connect to a GraphQL server and cache data efficiently. Which of the following code snippets correctly sets up the client and explains why this setup is best for performance?

hard

A. const client = new ApolloClient({ uri: 'https://api.example.com/graphql', cache: new InMemoryCache() }); // Efficient caching and server connection

B. const client = new ApolloClient({ uri: 'https://api.example.com/graphql' }); // No cache used, faster queries

C. const client = new ApolloClient({ cache: new InMemoryCache() }); // No server URI, so no connection

D. const client = ApolloClient({ uri: 'https://api.example.com/graphql', cache: new InMemoryCache() }); // Missing 'new' keyword

Solution

1. Step 1: Confirm correct Apollo Client instantiation

   const client = new ApolloClient({ uri: 'https://api.example.com/graphql', cache: new InMemoryCache() }); // Efficient caching and server connection uses 'new ApolloClient' with both 'uri' and 'cache' properly set, which is required for connection and caching.

2. Step 2: Understand why caching improves performance

   Using 'InMemoryCache' stores query results locally, reducing network requests and speeding up data access.

3. Final Answer:

   const client = new ApolloClient({ uri: 'https://api.example.com/graphql', cache: new InMemoryCache() }); // Efficient caching and server connection -> Option A

4. Quick Check:

   Use 'new ApolloClient' with 'uri' and 'InMemoryCache' for best performance [OK]

Hint: Always use 'new ApolloClient' with 'uri' and 'InMemoryCache' [OK]

Common Mistakes:

• Omitting cache reduces performance
• Missing 'new' causes errors
• Not specifying server URI prevents connection