SwiftUI vs. UIKit is the iOS development version of the classic tabs vs. spaces debate. Everyone has a strong preference. But what if you’re still on the fence?
Do you experiment with SwiftUI’s novel declarative approach, or rely on UIKit’s battle-tested foundation?
UIKit offers battle-tested stability and granular control, while SwiftUI promises a more intuitive development experience with its declarative syntax and cross-platform capabilities.
Making the right choice isn’t just about following trends – it’s about understanding how each framework’s strengths and limitations align with your project’s long-term goals and development priorities.
What is UIKit?
UIKit is Apple’s framework for building iOS user interfaces. Specifically, it’s the foundation for designing and managing every visual and interactive element in an iOS app—buttons, text fields, animations, and navigation.
Definition and purpose
UIKit was introduced in 2008 with iPhone OS 2.0 to simplify the development of interactive and visually-rich iPhone applications. It came with pre-built components to help developers manage inputs and create smooth screen transitions. The idea was to bridge the gap between an app’s functionality and its user-facing interface.
Features and capabilities
UIKit was built on Objective-C, an extension of the C programming language that introduced object-oriented programming and was later adapted for Swift. As the iOS development community grew in complexity over the years, UIKit evolved with it and expanded to support tvOS.
Among the UIKit features that bring iOS apps to life are:
- Touch gestures (taps, swipes, pinches) with UIGestureRecognizer.
- Responsive designs with Auto Layout for different screen sizes and orientations.
- Interactive animations with UIView.animate and UIViewPropertyAnimator.
- Complex data presentation with UITableView and UICollectionView.
- Multitasking with split-view controllers and drag-and-drop.
- App state restoration with built-in state management
- Accessibility with UIAccessibility
- System events like orientation changes and memory warnings.
UIKit pros
UIKit has been the foundation of iOS app development for over 10 years, so it’s no surprise it’s the go-to UI framework. Here are some of the benefits:
- Huge documentation and community support
- High level of control for custom app designs
- Support for older iOS versions
- Integration with Objective-C
- Visual design tools like Storyboards and Interface Builder
- Multiple state management options to handle app lifecycle events
UIKit cons
UIKit isn’t without its drawbacks. Here are some of the limitations developers may face:
- Steep learning curve, especially with imperative programming concepts
- Verbose and repetitive code compared to SwiftUI
- Manual work to maintain responsive designs across devices
- No cross-platform support outside of Apple’s ecosystem
- Incremental updates
- Limited built-in reactive programming features
What is SwiftUI?
SwiftUI is Apple’s new framework for building user interfaces across its ecosystem. It was introduced in 2019 with iOS SDK 13. This framework takes a different approach to UI development by simplifying it with a declarative programming model.
Definition and purpose
SwiftUI moves away from UIKit’s imperative programming style and introduces a declarative model. In this model, you describe what you want the UI to look like, and the system takes care of the how.
For example, instead of manually updating each part of the UI, you describe how the interface should respond to changes in the underlying data, and SwiftUI takes care of the rest automatically. No extra boilerplate code needed.
Features and capabilities
SwiftUI’s integration with Xcode Previews lets you see and adjust your interface in real-time so you don’t have to build and run the app to see the changes.
Beyond that, it’s cross-platform, so it supports macOS, watchOS, tvOS, and other Apple devices and has one codebase across all devices. It also has built-in accessibility features like VoiceOver, dynamic type, and Combined for handling asynchronous data.
SwiftUI pros
SwiftUI makes UI development faster and more intuitive and lets you create functional and beautiful apps. Here’s what developers love:
- Declarative syntax for less code and less repetition
- Live Previews in Xcode for instant updates
- Simplified state management
- Cross-platform for iOS, macOS, watchOS and tvOS
- Built-in accessibility that adapts to system settings like VoiceOver
- Tight integration with Combine for asynchronous data handling
- Adaptive layouts
SwiftUI cons
SwiftUI’s focus on simplicity and modern design is great, but sometimes it means sacrificing flexibility and compatibility. Here are some of the drawbacks:
- No backward compatibility: only supports iOS 13 and later
- Smaller community and fewer resources
- Less control for highly custom or fine-tuned UI elements
- Still evolving with potential breaking changes and limited advanced use case support
- Fewer third-party libraries than UIKit
- Debugging challenges due to it’s declarative nature
- Steep learning curve for those new to declarative or reactive programming
SwiftUI vs. UIKit in iOS App Development
Let’s compare SwiftUI and UIKit across programming styles, learning curves, performance, and compatibility.
Programming paradigm
When comparing UIKit and SwiftUI, the biggest difference is in the programming paradigm.
| Aspect | SwiftUI | UIKit |
| Approach | Declarative – You describe what the UI should look like, and SwiftUI takes care of the rest. | Imperative – You provide step-by-step instructions on how the UI should behave and respond to changes. |
| UI Updates | Reacts to state changes automatically. | Requires manual updates when state changes. |
| Code Management | Simplifies state-driven designs with @State and @Binding. | Relies on delegation, callbacks, and manual management. |
Code simplicity and readability
When it comes to code simplicity and readability, SwiftUI and UIKit are very different; here’s how:
| Aspect | SwiftUI | UIKit |
| Syntax | Clean and concise; describes what the UI should look like. | Verbose; requires step-by-step instructions for layout and behavior. |
| Readability | Minimal boilerplate code and focus on clarity. | Requires detailed layout constraints for even basic views. |
| Layout Management | Intuitive stacks (HStack, VStack, ZStack) with modifiers for alignment and spacing. | Depends on Auto Layout and NSLayoutConstraint APIs. |
| Code Example (Basic View) | swift struct ContentView: View { var body: some View { Text(“Hello, SwiftUI!”) .font(.title) .padding() } } | swift class ViewController: UIViewController { override func viewDidLoad() { super.viewDidLoad() let label = UILabel() label.text = “Hello, UIKit!” label.font = UIFont.systemFont(ofSize: 24) label.translatesAutoresizingMaskIntoConstraints = false view.addSubview(label) NSLayoutConstraint.activate([label.centerXAnchor.constraint(equalTo: view.centerXAnchor), label.centerYAnchor.constraint(equalTo: view.centerYAnchor)]) } } |
Performance and flexibility
SwiftUI and UIKit bring different superpowers regarding performance and flexibility—one’s fast, the other’s flexible. Here’s how they compare:
| Aspect | SwiftUI | UIKit |
| Prototyping | Great for rapid prototyping and quick iterations | Slower due to verbose code and manual setups |
| UI Design | Limited control; good for simple layouts | Full control for complex custom designs |
| Performance | Struggles with complex apps or older devices | Optimized for high-performance apps |
| Iterative Development | Live Previews | Full builds for testing |
Learning curve
Here’s how SwiftUI and UIKit compare when it comes to learning:
| Aspect | SwiftUI | UIKit |
| Beginner Friendliness | Easier; simple syntax and minimal boilerplate code | Complex for beginners; requires detailed configuration |
| Learning Resources & Community | Few tutorials and third-party resources; smaller community | Extensive documentation and tons of online tutorials; mature community |
| Ease of Debugging | Harder due to abstraction | Easier with explicit step-by-step control |
Compatibility and updates
SwiftUI and UIKit are very different when it comes to compatibility and Apple’s focus on iOS development trends:
| Aspect | SwiftUI | UIKit |
| iOS Version Support | Requires iOS 13+ | Supports all iOS versions since iOS 2.0 |
| Apple’s Long-Term Focus | Main updates | Stable but no major updates |
| Future-Proofing | Cross-platform development and modern app architecture | iOS only, limited cross-platform |
iOS Development: When to use SwiftUI vs. UIKit
It all comes down to your project and your role as an iOS engineer. And if you’re stuck, you can always use them together in the same system.
SwiftUI use cases
Here’s where SwiftUI is good for.
- Rapid prototyping or new apps for iOS 13+ with minimal setup.
- Medium complexity apps that need to be built fast without custom design.
- Cross-platform designs across Apple platforms, like iOS, macOS, watchOS and tvOS.
UIKit use cases
Here’s when you’d choose UIKit.
- Advanced or custom UI components, especially those that require professional UI design services.
- To maintain or update existing UIKit apps.
- When you need to support older iOS versions.
Moving from UIKit to SwiftUI
Are you thinking of making the leap? With the right approach (and potentially hiring iOS developers), you can modernize your app and make future updates much easier.
Migration challenges
Moving from UIKit to SwiftUI requires a new way of thinking. And since SwiftUI’s declarative model differs from UIKit’s step-by-step imperative approach, it takes time (and a big learning curve) to get used to the automatic updates and data-driven UI.
Refactoring existing UIKit code is another obstacle. Legacy code heavily depends on UIKit’s view hierarchies and Auto Layout, which don’t translate directly to SwiftUI’s stacks and modifiers. So, the challenge is to modernize your app without breaking its core.
Transition strategies
Moving to SwiftUI doesn’t have to be an all-or-nothing decision. You can use the strengths of both frameworks and transition gradually. Here’s how:
- Use SwiftUI for new features and keep existing UIKit components.
- Maximize interoperability by embedding SwiftUI views in UIKit or vice versa.
- Focus on features that benefit from SwiftUI.
- Start with small components like buttons or headers before migrating entire screens.
- Prototype to test and iterate on ideas using SwiftUI.
- Learn declarative programming.
- Refactor in phases to align existing UIKit code with SwiftUI concepts.
- Follow SwiftUI’s updates and best practices.
Summary
SwiftUI and UIKit are two of the best iOS development tools. They have different superpowers. The former simplifies development with its modern declarative approach, while the latter provides precision and reliability.
In the end, it all comes down to your iOS project and your experience level. So, if you need fast prototype results and cross-platform harmony, the answer is SwiftUI.
Struggling with complex designs or legacy apps? UIKit’s got you covered, and you’ll get more flexibility, too. And you can always use them together for the ultimate combo.
FAQs
What’s the main difference between SwiftUI and UIKit?
The main difference between SwiftUI and UIKit is the programming model. SwiftUI is declarative, where you describe what the UI should be, and it updates automatically. UIKit is imperative, as you define how the UI should behave step by step, including managing updates and interactions.
Is SwiftUI replacing UIKit?
No, UIKit is still being used alongside SwiftUI. While Apple is pushing SwiftUI as the future of UI development, UIKit is still very relevant for maintaining existing apps. In fact, it still handles complex designs and supports older iOS versions.
Can I use SwiftUI and UIKit together?
Yes, SwiftUI and UIKit can be used together through interop. You can use UIViewRepresentable or UIViewControllerRepresentable to embed UIKit in SwiftUI and UIHostingController to add SwiftUI views to UIKit projects.
Which one is better for beginners: SwiftUI or UIKit?
SwiftUI is better for beginners because of its declarative syntax, simplifying UI creation with less code and fewer technical concepts like auto layout or delegation. It’s easier to learn and great for prototyping. UIKit while more complex gives you a deeper understanding of how UIs are built and managed through concepts like view hierarchies and constraints.
