💭 Fix Synchronization Issues for macOS Apps Using Core Data/SwiftData

TL;DR: macOS apps using Core Data/SwiftData for synchronization must manually include CloudKit.framework in the project’s dependencies. Unlike iOS, macOS does not automatically include this framework, leading to sync failures in TestFlight or release versions. Add CloudKit.framework in “Frameworks, Libraries, and Embedded Content,” rebuild the app, and verify functionality in release environments to resolve the issue.

Background

Core Data and SwiftData offer robust CloudKit-based data synchronization capabilities, widely used in iOS and macOS applications supporting multi-device sync. However, many developers encounter issues with synchronization functionality not working properly on macOS when extending iOS apps with sync support to the macOS platform.

This article analyzes the root cause of this issue and provides a detailed solution.

Problem Description

When using Core Data/SwiftData synchronization features on macOS, developers may encounter the following issues:

1. Synchronization Anomalies Between Devices:
   • Data synchronizes normally between iOS devices.
   • Data fails to synchronize between iOS and macOS devices or between macOS devices.
2. Correct Permission Configurations:
   • macOS has the necessary permissions correctly configured (e.g., iCloud sync permissions), but the issue persists.
3. Inconsistent Behavior in Debug vs. Release Environments:
   • Sync works as expected when running the macOS app in Xcode debug mode.
   • Sync fails in versions distributed via TestFlight or the App Store.

Root Cause

The core issue is that: macOS apps using Core Data/SwiftData for data synchronization must manually add CloudKit.framework to the project dependencies.

In iOS apps, CloudKit.framework is automatically included in the build. However, this is not the case for macOS projects. If this dependency is not manually added, TestFlight and release versions will fail to access CloudKit services, resulting in synchronization failure.

Solution

Step 1: Check and Add CloudKit.framework

Ensure that CloudKit.framework is correctly added as a dependency in your macOS project’s build settings:

1. Open your project settings and navigate to “Frameworks, Libraries, and Embedded Content”.
2. Click the “+” button, search for, and select CloudKit.framework.

Here’s a visual example of the configuration:

Step 2: Rebuild and Verify

1. Ensure there are no other configuration issues related to synchronization.
2. Rebuild the project and test it via TestFlight or the release version.

After completing the steps above, the cloud synchronization functionality in your macOS app should work as expected.

Notes

• Special Consideration for Catalyst Projects: If you are using Catalyst to port an iOS app to macOS, you must also manually add the CloudKit.framework dependency.
• App Store Review Behavior: macOS apps missing the CloudKit.framework can still pass App Store review. This leniency may lead developers to overlook the root cause, so extra attention is needed.

Further Reading

The following resources provide in-depth insights into Core Data and CloudKit, helping developers better understand synchronization mechanisms:

• Core Data with CloudKit: Syncing Local Database to iCloud Private Database
• Core Data with CloudKit: Sharing Data in the iCloud