Unlocking SwiftUI at Airbnb: A Deep Dive into Modern UI Development

Imagine building a house where every room is designed by a different architect, each using their own unique blueprint. Now, imagine trying to make all those rooms feel like they belong to the same home. This is the challenge Airbnb faced with its iOS app, where multiple UI frameworks and legacy codebases created inconsistency and inefficiency. Enter SwiftUI, Apple’s declarative UI framework, which promised to streamline development and unify the user experience.

In this blog post, we’ll explore how Airbnb embraced SwiftUI, the technical challenges they overcame, and the lessons they learned along the way. Whether you’re an iOS developer, a product manager, or a tech enthusiast, this deep dive will provide valuable insights into modern UI development.

Why SwiftUI?

SwiftUI, introduced by Apple in 2019, is a declarative framework for building user interfaces across Apple platforms. Unlike UIKit, which uses an imperative approach, SwiftUI allows developers to describe what the UI should do, rather than how it should do it. This shift brings several advantages:

• Declarative Syntax: Simplifies UI development by reducing boilerplate code.
• Cross-Platform Compatibility: Build interfaces for iOS, macOS, watchOS, and tvOS with a single codebase.
• Real-Time Previews: See changes instantly with Xcode’s live preview feature.
• Improved Maintainability: Declarative code is easier to read, debug, and update.

For Airbnb, adopting SwiftUI was a strategic move to modernize their iOS app, improve developer productivity, and deliver a more consistent user experience.

The Journey to SwiftUI Adoption

1. Assessing the Existing Codebase

Airbnb’s iOS app was built on a mix of UIKit and React Native, resulting in a fragmented codebase. The team needed to evaluate whether SwiftUI could coexist with these frameworks and how to migrate gradually without disrupting the user experience.

Key Considerations:

• Compatibility: SwiftUI seamlessly integrates with UIKit, allowing incremental adoption.
• Performance: Early testing showed that SwiftUI performed well for most use cases but had limitations with highly dynamic views.
• Team Readiness: Developers needed training to transition from imperative to declarative programming.

2. Building a Proof of Concept

To validate SwiftUI’s potential, Airbnb created a proof of concept (PoC) for a new feature. The PoC demonstrated that SwiftUI could:

• Reduce development time by 30% compared to UIKit.
• Deliver a smoother and more responsive user experience.
• Enable faster iteration with live previews.

3. Gradual Integration

Instead of rewriting the entire app in SwiftUI, Airbnb adopted a phased approach:

• New Features: All new features were built using SwiftUI.
• Refactoring: Existing components were gradually migrated to SwiftUI during feature updates.
• Hybrid Approach: UIKit and SwiftUI components coexisted, with bridges like UIHostingController facilitating integration.

Technical Challenges and Solutions

Challenge 1: Bridging UIKit and SwiftUI

While SwiftUI is powerful, it doesn’t yet cover all the functionalities of UIKit. Airbnb used UIHostingController to embed SwiftUI views within UIKit-based screens and vice versa.

import SwiftUI
import UIKit

struct SwiftUIView: View {
    var body: some View {
        Text("Hello, SwiftUI!")
    }
}

class UIKitViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        let swiftUIView = SwiftUIView()
        let hostingController = UIHostingController(rootView: swiftUIView)
        addChild(hostingController)
        view.addSubview(hostingController.view)
        hostingController.view.frame = view.bounds
    }
}

Challenge 2: Performance Optimization

SwiftUI’s declarative nature can sometimes lead to performance bottlenecks, especially with complex views. Airbnb addressed this by:

• Using @State and @Binding efficiently to minimize unnecessary view updates.
• Leveraging LazyVStack and LazyHStack for lazy loading of content.
• Profiling and optimizing expensive operations using Xcode’s Instruments tool.

Challenge 3: Ensuring Consistency

With multiple teams working on the app, maintaining a consistent design system was crucial. Airbnb created a shared SwiftUI component library, ensuring that all teams used the same buttons, cards, and typography.

Lessons Learned

1. Start Small: Begin with a PoC or a small feature to validate the technology and build team confidence.
2. Invest in Training: Provide resources and training to help developers transition to declarative programming.
3. Adopt Incrementally: A gradual migration minimizes risks and allows for continuous learning.
4. Leverage Hybrid Approaches: Use bridging tools to integrate SwiftUI with existing frameworks.
5. Focus on Developer Experience: Tools like live previews and declarative syntax can significantly boost productivity.

The Future of SwiftUI at Airbnb

Airbnb’s adoption of SwiftUI is still ongoing, but the results so far are promising. The team plans to:

• Expand the use of SwiftUI to more features and screens.
• Contribute to the SwiftUI community by open-sourcing reusable components.
• Continue optimizing performance and developer workflows.

By embracing SwiftUI, Airbnb is not only future-proofing its app but also setting a benchmark for modern UI development. You can read more details here: Unlocking SwiftUI at Airbnb.