Push notifications with FCM in React Native - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does FCM stand for in mobile development?

FCM stands for Firebase Cloud Messaging. It is a service that helps send push notifications to mobile apps.

beginner

Why do we need to ask user permission for push notifications on iOS?

iOS requires apps to ask users for permission before sending push notifications to respect user privacy and control.

intermediate

What is the role of a device token in FCM push notifications?

A device token is a unique ID that identifies a device to FCM so it knows where to send the notification.

intermediate

Name one React Native library commonly used to handle FCM push notifications.

One popular library is '@react-native-firebase/messaging' which helps integrate FCM in React Native apps.

beginner

What is a common step to test push notifications during development?

You can use Firebase Console to send test notifications to your app using the device token.

What is the first step to receive push notifications in a React Native app using FCM?

A Request user permission for notifications

B Send a notification from Firebase Console

C Install a React Native navigation library

D Create a new Firebase project

You must first ask the user for permission to receive notifications before you can get a device token.

Which platform requires explicit user permission for push notifications?

A Android

B iOS

C Both Android and iOS

D Neither Android nor iOS

iOS requires explicit user permission, while Android grants it by default.

What does the device token represent in FCM?

A App version number

B User's email address

C Unique device identifier for sending notifications

D Firebase project ID

The device token uniquely identifies the device to receive push notifications.

Which React Native package is commonly used to handle FCM messaging?

A react-navigation

B axios

C redux

D @react-native-firebase/messaging

The '@react-native-firebase/messaging' package helps integrate FCM push notifications.

Where can you send test push notifications to your app during development?

A Firebase Console

B Google Play Store

C App Store Connect

D React Native CLI

Firebase Console allows you to send test notifications to your app using device tokens.

Explain the process of setting up push notifications with FCM in a React Native app.

Think about the steps from Firebase setup to receiving a notification on the device.

Describe why user permission is important for push notifications and how it differs between iOS and Android.

Consider platform rules and user control over notifications.

Practice

1. What is the main purpose of Firebase Cloud Messaging (FCM) in a React Native app?

easy

A. To create UI components

B. To store user data locally

C. To send push notifications to the app users

D. To manage app navigation

Solution

1. Step 1: Understand FCM's role

   FCM is a service designed to send push notifications to apps.

2. Step 2: Compare options

   Only To send push notifications to the app users describes sending push notifications, which is FCM's main purpose.

3. Final Answer:

   To send push notifications to the app users -> Option C

4. Quick Check:

   FCM = Push notifications [OK]

Hint: FCM is about messaging, not UI or storage [OK]

Common Mistakes:

• Confusing FCM with local data storage
• Thinking FCM manages UI or navigation
• Assuming FCM is for database operations

2. Which React Native Firebase method is used to get the device token for FCM push notifications?

easy

A. messaging().requestPermission()

B. messaging().getToken()

C. messaging().sendMessage()

D. messaging().subscribeToTopic()

Solution

1. Step 1: Identify token retrieval method

   The method to get the device token is messaging().getToken().

2. Step 2: Eliminate other options

   requestPermission() asks user permission, sendMessage() sends messages, subscribeToTopic() subscribes to topics.

3. Final Answer:

   messaging().getToken() -> Option B

4. Quick Check:

   Get token = getToken() [OK]

Hint: Get token with getToken(), not requestPermission() [OK]

Common Mistakes:

• Using requestPermission() to get token
• Confusing sendMessage() with token retrieval
• Mixing subscribeToTopic() with token methods

3. What will be the output of this code snippet in a React Native app using FCM?

import messaging from '@react-native-firebase/messaging';

async function getToken() {
  const token = await messaging().getToken();
  console.log(token);
}

getToken();

medium

A. Logs the device's FCM token string to the console

B. Throws a syntax error due to missing await

C. Logs 'undefined' because getToken() returns nothing

D. Throws a runtime error because messaging() is undefined

Solution

1. Step 1: Analyze async function behavior

   The function awaits messaging().getToken(), which returns the device token string.

2. Step 2: Understand console.log output

   It logs the token string, not undefined or error, assuming messaging is imported correctly.

3. Final Answer:

   Logs the device's FCM token string to the console -> Option A

4. Quick Check:

   getToken() returns token string [OK]

Hint: Await getToken() to get token string, then log it [OK]

Common Mistakes:

• Forgetting await causing Promise logged
• Assuming getToken() returns undefined
• Not importing messaging correctly

4. You wrote this code to request permission for notifications but it doesn't work as expected:

import messaging from '@react-native-firebase/messaging';

messaging().requestPermission();

What is the likely problem?

medium

A. requestPermission() is not a valid method

B. You need to import notifications instead of messaging

C. You must call getToken() before requestPermission()

D. You forgot to await the requestPermission() call

Solution

1. Step 1: Check async method usage

   requestPermission() returns a Promise and should be awaited to complete permission request.

2. Step 2: Identify missing await effect

   Without await, the permission request may not finish before next steps, causing unexpected behavior.

3. Final Answer:

   You forgot to await the requestPermission() call -> Option D

4. Quick Check:

   Await async calls like requestPermission() [OK]

Hint: Always await async permission requests [OK]

Common Mistakes:

• Not awaiting async permission calls
• Thinking requestPermission() is invalid
• Calling getToken() before permission

5. You want to send a push notification only if the user has granted permission. Which code snippet correctly checks permission and then gets the FCM token in React Native?

hard

A. const authStatus = await messaging().requestPermission();
if (authStatus === messaging.AuthorizationStatus.AUTHORIZED) {
const token = await messaging().getToken();
console.log(token);
}

B. const token = await messaging().getToken();
if (token) {
await messaging().requestPermission();
console.log(token);
}

C. await messaging().getToken();
await messaging().requestPermission();
console.log('Permission and token done');

D. messaging().requestPermission();
messaging().getToken();
console.log('Permissions requested and token fetched');

Solution

1. Step 1: Check permission before token

   const authStatus = await messaging().requestPermission(); if (authStatus === messaging.AuthorizationStatus.AUTHORIZED) { const token = await messaging().getToken(); console.log(token); } requests permission and checks if authorized before getting token.

2. Step 2: Verify async and order correctness

   const authStatus = await messaging().requestPermission(); if (authStatus === messaging.AuthorizationStatus.AUTHORIZED) { const token = await messaging().getToken(); console.log(token); } awaits both calls and uses correct AuthorizationStatus check.

3. Final Answer:

   const authStatus = await messaging().requestPermission(); if (authStatus === messaging.AuthorizationStatus.AUTHORIZED) { const token = await messaging().getToken(); console.log(token); } -> Option A

4. Quick Check:

   Check permission first, then get token [OK]

Hint: Request permission first, then get token if authorized [OK]

Common Mistakes:

• Getting token before permission
• Not awaiting async calls
• Ignoring authorization status check