Offline Mode: Key Strategies and Benefits for iOS – DZone

Why Should You Support Offline Mode in Mobile Apps?

Offline-first apps are designed to function effectively even when there is no internet connection. There are some primary reasons why supporting offline mode is essential for mobile apps:

• Improved user experience and reach: Users can continue using the app even when there is no internet connection. Offline support attracts more users in areas of low connectivity or users that travel often thereby increasing availability
• Increased user engagement and retention: By providing a consistent experience regardless of connectivity, offline mode helps build user trust and encourages longer engagement. This enhanced reliability can lead to higher user retention rates.
• Lower battery consumption: Offline apps consume less battery power. This is because they don’t continuously poll the network or fetch remote data, which can be energy-intensive
• Reduced downtime: Supporting offline apps would also help reduce downtime caused by network failures or server issues, maintaining access to the feature.

Key Strategies for Supporting Offline Mode in Apps

There are various strategies to gracefully support offline mode in mobile apps:

1. Data Caching

Description

In data caching, developers download and store the required data on the device when it is connected, thus allowing offline access of the feature.

How To Implement

There are multiple solutions available that allow local storage like Core Data, SwiftData, Realm, Couchbase Mobile, SQLite or URLCache.

Benefits

Caching significantly improves the performance of the app and minimizes the data usage by reducing the repeated requests made to the server for the same information.

Key Considerations

Developers should implement cache invalidation to keep data up-to-date. Moreover, implementing caching can consume device storage. As developers, it’s our responsibility to manage caching efficiently to avoid excessive storage usage.

2. Data Synchronization

Description

In data synchronization, developers sync local data with the server when connectivity is restored. There could be some user actions on the app which updates the state of the app, and it is important to register that on our backend. Therefore, when the user regains connectivity, it is essential to sync the local data with the server to update the remote database.

How To Implement

Developers can use background tasks, scheduled syncs, or URLSession to make the sync request to the server.

Benefits

This will ensure data consistency across devices.

Key Considerations

Handle network failures gracefully during sync operations, provide user feedback, and use queues to manage sync operations in the correct order without overwhelming the server.

3. Conflict Resolutions

Description

This strategy focuses on addressing changes that were made online vs offline.

How To Implement

To implement conflict resolution, developers should focus on defining strategies like “last write wins” or “merge changes” to make sure that the right data synced with our backend.

Benefits

This helps prevent data loss and also maintains data integrity. 

Key Considerations

It is important to update the user about the conflict resolution in case that affects their personal data. It is also important to think about various flows that would require conflict resolution.

4. Optimistic UI Updates

Description

In this strategy, developers update the UI based on the user actions without making a server request or waiting for a server response.

How To Implement

To implement this, developers should apply changes to the UI by storing the data locally first, and then asynchronously sync those changes with the server.

Benefits

This strategy ensures a smooth user experience by reducing the impact of network latency.

Key Considerations

Be prepared to handle cases where optimistic updates fail due to network issues or server-side validation errors.

5. User-Controlled Synchronization

Description

In strategy, developers allow the user to manually trigger a sync to ensure that the data is registered on the backend. During the offline mode, for obvious reasons, this isn’t possible, but is once the user is back online. Until then, developers can possibly cache the data.

How To Implement

Developers can provide some settings or options in the app for users to control sync frequency and also a UI element may trigger sync on tap.

Benefits

The main advantage of this strategy is giving users control over whether they want to initiate the sync, providing them more control over the app processes.

Key Consideration

It is important to clearly communicate with the user about the manual sync since they might assume that data auto-syncs. Also, implement UI to provide user feedback on sync status and progress.

6. Enable Users To Download Content for Offline Access

Description

Enable users to manually download specific content.; for example, download the music file to play it later in low or no connection areas. 

How To Implement

Provide a button or some UI element within the app to download the required data for offline use.

Benefits

This gives users control over what content they want available offline.

Key Consideration

It is important to ensure that the users are aware of the storage implications of downloading content. It is also essential to provide options to manage or delete downloaded files to free up space within the app itself.

How To Plan for Support Offline Mode in Mobile Apps in Each Stage of the Software Development Lifecycle

1. Requirements Gathering

• What to do: Developers should start by gathering all the requirements for the app and identifying features that should support offline features. Developers should consult with various stakeholders, including users, to understand their needs and requirements. 
• Actions: Conduct interviews with stakeholders and intended users to identify key features of the app. Identify the features that should support offline mode and discuss the scope of those features.

2. Design

• What to do: In this stage, developers want to design the app architecture to support offline mode for the identified features of the app.
• Actions: Developers should start by choosing the appropriate data storage solution and designing data models to support offline storage. Then, they should develop a strategy for data synchronization, conflict resolution, and error handling. Developers also cover designing UI elements that provide feedback to users about offline status and available actions.
• Considerations: Developers should account for both offline and online modes of the app providing a seamless performance overall.

3. Development

• What to do: At this stage it is very obvious to focus on implementing the core offline features as part of the development process.
• Actions: One tool that you can use to simulate low network conditions is the Network Link Conditioner. Developers can also simulate low network conditions by disabling your Wi-Fi on a MacBook while testing on the simulator or by disabling the mobile network when testing on your device.
• Considerations: Testing offline mode can be tedious at times and can be overlooked, but it is essential to have a test plan to consistently test offline mode during the development stage.   

4. Testing

• What to do: Quality Assurance (QA) teams want to ensure complete test coverage of both offline and online features of the app 
• Actions: The QA team needs to build a comprehensive testing plan that ensures testing the offline mode for key features. They also want to perform unit testing, integration testing, and user acceptance testing specifically for offline scenarios before releasing the app.