Push notification integration in HLD - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a push notification in mobile apps?

A push notification is a message sent by an app to a user's device to provide updates or alerts, even when the app is not open.

beginner

Name two common services used for push notification delivery.

Firebase Cloud Messaging (FCM) and Apple Push Notification Service (APNs) are two common services used to send push notifications to Android and iOS devices respectively.

intermediate

What is a device token in push notification integration?

A device token is a unique identifier assigned to a device by the push notification service, used to target that specific device when sending notifications.

beginner

Why do apps need user permission for push notifications?

Apps need user permission to respect privacy and avoid unwanted interruptions. Users control whether they want to receive notifications.

intermediate

What is the role of a notification payload?

The notification payload contains the message content and data sent from the server to the device, defining what the notification shows and how it behaves.

Which service is used to send push notifications to Android devices?

A Firebase Cloud Messaging (FCM)

B Apple Push Notification Service (APNs)

C Google Maps API

D SQLite

Firebase Cloud Messaging (FCM) is the service for Android push notifications.

What must an app request from the user before sending push notifications?

A User permission

B User password

C User location

D User email

Apps must ask for user permission to send push notifications.

What does a device token represent?

A The user's password

B A unique device identifier for notifications

C The app version number

D The device's battery level

Device token uniquely identifies the device for push notifications.

Which part of a push notification contains the message text?

A App icon

B Device token

C User permission

D Notification payload

The notification payload includes the message content.

When can a push notification be received by the user?

A Only during app installation

B Only when the app is open

C Even when the app is closed

D Only when the device is charging

Push notifications can arrive even if the app is not running.

Explain the steps to integrate push notifications in a mobile app.

Think about what happens from app start to notification display.

Describe why user permission is important for push notifications.

Consider the user's experience and privacy.

Practice

1. What is the main purpose of integrating push notifications in a mobile app?

easy

A. To keep users updated even when the app is closed

B. To increase app size significantly

C. To slow down the app performance

D. To disable user interaction

Solution

1. Step 1: Understand push notification purpose

   Push notifications are messages sent to users to keep them informed or engaged.

2. Step 2: Identify correct purpose in options

   Only To keep users updated even when the app is closed correctly states that notifications keep users updated even when app is closed.

3. Final Answer:

   To keep users updated even when the app is closed -> Option A

4. Quick Check:

   Push notifications = keep users updated [OK]

Hint: Push notifications inform users outside the app [OK]

Common Mistakes:

• Thinking notifications increase app size
• Believing notifications slow app down
• Assuming notifications disable interaction

2. Which code snippet correctly requests user permission for push notifications in a mobile app?

easy

A. requestNotificationPermission();

B. enablePushNotifications();

C. askUserForNotificationPermission();

D. requestPermissionForNotifications();

Solution

1. Step 1: Identify standard permission request method

   Common method names include 'requestPermissionForNotifications' to ask user consent.

2. Step 2: Compare options for correct syntax

   requestPermissionForNotifications(); uses a clear, standard naming pattern for requesting permission.

3. Final Answer:

   requestPermissionForNotifications(); -> Option D

4. Quick Check:

   Permission request method = requestPermissionForNotifications() [OK]

Hint: Look for method names starting with 'requestPermission' [OK]

Common Mistakes:

• Using method names that don't request permission
• Confusing enabling notifications with requesting permission
• Using non-standard or undefined method names

3. Given this code snippet handling a push notification:

onNotificationReceived(notification) {
  if (notification.type === 'message') {
    showAlert(notification.title);
  }
}

What happens when a notification with type 'message' arrives?

medium

A. An alert with the notification title is shown

B. The notification is ignored

C. The app crashes due to missing handler

D. A log is printed but no alert

Solution

1. Step 1: Analyze the notification type check

   The code checks if notification.type equals 'message'.

2. Step 2: Understand the action on matching type

   If true, it calls showAlert with notification.title, displaying an alert.

3. Final Answer:

   An alert with the notification title is shown -> Option A

4. Quick Check:

   Type 'message' triggers alert display [OK]

Hint: Check condition and action inside notification handler [OK]

Common Mistakes:

• Assuming notification is ignored
• Thinking app crashes without error
• Confusing logging with alert display

4. Identify the error in this push notification handler code:

function handleNotification(notification) {
  if notification.isRead = false {
    displayNotification(notification);
  }
}

medium

A. Missing semicolon after function declaration

B. Using assignment '=' instead of comparison '==' in if condition

C. Incorrect function name 'handleNotification'

D. Notification object missing required fields

Solution

1. Step 1: Check the if condition syntax

   The condition uses '=' which assigns value instead of comparing.

2. Step 2: Identify correct comparison operator

   It should use '==' or '===' to compare values, not '='.

3. Final Answer:

   Using assignment '=' instead of comparison '==' in if condition -> Option B

4. Quick Check:

   Use '==' for comparison, not '=' [OK]

Hint: Remember '=' assigns, '==' compares in conditions [OK]

Common Mistakes:

• Confusing assignment and comparison operators
• Ignoring syntax errors in if statements
• Assuming function name causes error

5. You want to send a push notification only if the user has granted permission and the app is in background. Which logic correctly implements this?

hard

A. if (userPermissionGranted && appState !== 'background') { sendPushNotification(); }

B. if (userPermissionGranted || appState === 'background') { sendPushNotification(); }

C. if (userPermissionGranted && appState === 'background') { sendPushNotification(); }

D. if (!userPermissionGranted && appState === 'background') { sendPushNotification(); }

Solution

1. Step 1: Understand conditions for sending notification

   Notification should send only if permission is granted AND app is in background.

2. Step 2: Evaluate logical operators in options

   if (userPermissionGranted && appState === 'background') { sendPushNotification(); } uses '&&' (AND) correctly to check both conditions.

3. Final Answer:

   if (userPermissionGranted && appState === 'background') { sendPushNotification(); } -> Option C

4. Quick Check:

   Use AND (&&) to require both conditions [OK]

Hint: Use AND (&&) to combine required conditions [OK]

Common Mistakes:

• Using OR (||) instead of AND (&&)
• Negating permission incorrectly
• Checking wrong app state