Understanding the Problem
Reactive Binding Overhead
Fuse's reactive model updates the UI automatically when bound data changes. While this is powerful, in high-frequency update scenarios (e.g., sensor data, stock tickers), the continuous re-rendering can cause frame drops and memory spikes. Over time, excessive bindings can also lead to memory leaks if observers are not cleaned up.
Native Interop Risks
Fuse allows JavaScript to call native functions via Uno code. Without strict lifecycle control, native resources can remain allocated beyond their intended scope, leading to crashes or slowdowns in long-running sessions.
Background on Fuse Architecture
UX Markup and Uno Layer
Fuse uses UX files for UI structure, which compile into Uno code that interacts directly with native APIs. JavaScript logic runs in a V8 engine embedded in the app, with bindings to Uno for platform-specific features. Misalignment between UX and Uno lifecycles is a common cause of inconsistent UI state.
Threading Model
UI updates occur on the main thread, but JavaScript and native calls may run on background threads. Improper synchronization between threads can cause intermittent UI corruption or application freezes.
Diagnostic Approach
Step 1: Profile Reactive Updates
Use Fuse's --monitor and Uno performance profiling tools to track binding update frequency. Identify data sources that trigger high-frequency updates and evaluate if throttling is needed.
Step 2: Analyze Memory Allocation
On Android, use adb shell dumpsys meminfo and Android Studio Profiler; on iOS, use Xcode's Instruments. Compare JS heap usage with native heap usage to locate leaks in either layer.
Step 3: Thread Synchronization Audit
Check native Uno code for UI updates outside the main thread. Ensure any UI-affecting calls are dispatched correctly to the UI loop.
Step 4: UX-Native Lifecycle Review
Match UX component lifecycle hooks (OnNavigatedTo, OnNavigatedFrom) with native resource allocation and disposal to prevent orphaned resources.
Common Pitfalls
- Leaving observers bound after component disposal
- Triggering animations from background threads
- Holding native references in JS closures beyond lifecycle
- Overusing reactive bindings for high-frequency data without throttling
- Mismatched UX and Uno lifecycles
Step-by-Step Fixes
1. Clean Up Observers
Unsubscribe from all reactive observables when the component is destroyed.
// JavaScript example
var Observable = require("FuseJS/Observable");
var data = Observable();
var subscription = data.onValueChanged(function(val) {
console.log(val);
});
module.exports.dispose = function() {
subscription.unsubscribe();
}
2. Throttle High-Frequency Updates
Reduce render frequency by debouncing or batching updates.
// Debounce example
var Observable = require("FuseJS/Observable");
var source = Observable();
var throttled = source.debounce(200);
3. Ensure Main Thread UI Updates
Wrap native UI updates in main-thread dispatch calls.
// Uno example
Fuse.UpdateManager.PostAction(() => {
myUIElement.Value = "Updated safely";
});
4. Dispose Native Resources
In Uno, implement IDisposable for any class managing native handles and call dispose in UX lifecycle exit points.
5. Align UX and Native Lifecycle
Ensure OnNavigatedFrom triggers cleanup of any associated JS timers, observers, or native handles.
Best Practices for Prevention
- Audit bindings regularly and remove unused observers
- Limit high-frequency bindings to non-UI threads when possible
- Use Fuse Monitor to track performance regressions
- Test with low-end devices early in development to catch performance bottlenecks
- Encapsulate native interop logic with clear lifecycle boundaries
Conclusion
Fuse Open offers a powerful model for building cross-platform native apps with a unified UX and logic layer. However, in enterprise-scale projects, careful management of reactive bindings, threading, and native resources is critical to maintain performance and stability. By applying disciplined lifecycle handling and proactive profiling, teams can avoid subtle leaks, crashes, and slowdowns, ensuring their Fuse applications remain robust under heavy use.
FAQs
1. How can I detect if a memory leak is in JS or native code in Fuse?
Profile both JS and native heaps separately using platform tools. If native usage grows while JS heap is stable, the leak is likely in Uno or native code.
2. Does Fuse automatically clean up observers?
No. Observers must be explicitly unsubscribed during component disposal to avoid leaks.
3. How can I improve animation performance in Fuse?
Limit simultaneous animations, avoid unnecessary reactive bindings on animated properties, and batch updates where possible.
4. Can high-frequency data streams be handled safely?
Yes, by throttling updates, processing off the UI thread, and updating UI elements only when necessary.
5. Should all native interop be wrapped in Uno?
Yes. Uno provides type safety and lifecycle hooks that help prevent resource leaks and threading issues when calling native APIs.