How do I handle state changes in CoreRender?

Use coordinators to manage state—they are non-transient objects that hold data and call setNeedsReconcile() to trigger UI updates. This mirrors the CounterCoordinator example where count increments prompt reconciliation.

CoreRender or SwiftUI for a new iOS project?

Choose SwiftUI if targeting iOS 13+ and wanting full Apple support with native features. CoreRender is better for supporting older iOS versions (10+) or integrating declarative patterns into existing UIKit/Objective-C codebases without a full rewrite.

Can I use CoreRender with Objective-C?

Yes, CoreRender is compatible with Objective-C, allowing it to be used in mixed-language projects or pure Objective-C apps targeting iOS 10+. The README emphasizes this as a key feature for broader adoption.

How to animate views in CoreRender?

Animations rely on UIKit's system; you can animate properties within coordinators or use UIView animations by accessing concrete views via coordinators after reconciliation, though this might require manual intervention beyond the declarative API.

What's the performance impact of using CoreRender?

CoreRender uses efficient diffing and fine-grained recycling for performance, but in highly dynamic UIs with frequent updates, the reconciliation overhead could be noticeable compared to manually optimized imperative UIKit code.

How to debug when CoreRender doesn't update the UI?

Ensure setNeedsReconcile() is called after state changes in coordinators, and check the virtual DOM hierarchy for issues. Debugging may involve inspecting coordinator state and the reconciliation process, which lacks built-in tools compared to SwiftUI.

Open-Awesome

Render

Swift7.0.3

A SwiftUI-inspired declarative UI framework for UIKit with Flexbox layout, compatible with iOS 10+ and Objective-C.

GitHub

2.1k stars98 forks0 contributors

What is Render?

Render (CoreRender) is a declarative UI framework for UIKit that mimics SwiftUI's API, allowing developers to build user interfaces using a declarative syntax. It solves the problem of writing verbose, imperative UIKit code by introducing a virtual DOM-like reconciliation system that automatically updates the view hierarchy. The framework is compatible with iOS 10+ and Objective-C, making it suitable for projects that cannot yet adopt SwiftUI.

Target Audience

iOS developers working with UIKit who want to adopt declarative UI patterns without migrating to SwiftUI, especially those supporting iOS 10+ or mixed Objective-C/Swift codebases.

Value Proposition

Developers choose Render for its ability to bring SwiftUI-like development experience to older iOS versions, its efficient diffing and reconciliation engine, and seamless integration with existing UIKit projects. It offers a pragmatic path to modern UI development while maintaining compatibility.

Overview

UIKit a-là SwiftUI.framework [min deployment target iOS10]

Use Cases

Best For

Migrating UIKit codebases to declarative patterns without rewriting in SwiftUI
Building iOS apps that need to support iOS 10 and above with modern UI techniques
Integrating declarative UI components into existing Objective-C projects
Creating reusable UI components with fine-grained recycling for performance
Adopting Flexbox layout in UIKit-based applications
Bridging SwiftUI and UIKit in hybrid application architectures

Not Ideal For

Projects exclusively targeting iOS 13+ where SwiftUI is fully supported and preferred
Teams requiring minimal dependencies or avoiding third-party layout engines like Yoga
Apps with highly complex, performance-critical animations that need fine-tuned imperative control
Developers needing extensive community plugins or templates, as Render has a smaller ecosystem

Pros & Cons

Pros

Declarative UIKit Development

Enables SwiftUI-like declarative syntax for UIKit, reducing imperative code and automating view updates through diffing and reconciliation, as shown in the Counter-Example DSL.

Broad iOS Compatibility

Supports iOS 10+ and Objective-C, making it suitable for legacy projects that cannot yet adopt SwiftUI, as stated in the README's compatibility claims.

Efficient Layout with Flexbox

Integrates Facebook's Yoga engine for reliable Flexbox-based layouts, a battle-tested solution that handles complex UI arrangements robustly.

Hybrid SwiftUI Integration

Allows embedding Render nodes in SwiftUI views via CoreRenderBridgeView, facilitating gradual migration or mixed-framework approaches, as demonstrated in the SwiftUI example.

Cons

Third-Party Dependency

Relies on Facebook's Yoga for layout, which adds an external dependency that could increase binary size or introduce compatibility issues in tightly controlled environments.

Learning Curve for Imperative Developers

Requires adoption of declarative patterns and the coordinator model, which can be unfamiliar and challenging for UIKit veterans accustomed to direct view manipulation and lifecycle management.

Limited SwiftUI Feature Parity

Does not implement all SwiftUI features or newer iOS APIs, so advanced UI capabilities like some animations or modifiers might be missing or require workarounds.

Frequently Asked Questions

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