The Great Migration: Should You Switch from UIKit to SwiftUI?

SwiftUI is a popular UI toolkit developed and released by Apple in 2019. Seen as an evolution in iOS development from UIKit, SwiftUI has several new features and improvements relevant to modern app dev teams. Many teams who haven’t yet switched to SwiftUI from UIKit are starting to consider migration. We’ll discuss the benefits and potential drawbacks of migration, how to know if you should migrate, and more.

What is SwiftUI?

Designed as a low-code alternative for developing better application interfaces, SwiftUI leverages declarative syntax for fast and simple app development. Launched with support for all Apple platforms (iOS, macOS, watchOS, and tvOS), SwiftUI has continued to evolve over the last five years into a robust platform to help developers create applications with rich features and great user experiences.

SwiftUI 5.0 was released in 2023 and was seen as a major redesign to the framework. In addition to upgraded visual effects and gestures, Apple also introduced SwiftData, a brand-new framework for managing data within apps.

UIKit vs. Swift UI: Strengths and Weaknesses

As SwiftUI has been seen as a replacement or evolution from UIKit, developers must often consider each framework’s strengths and weaknesses when deciding whether or not to migrate.

UIKit

UIKit is a mature and stable framework – it’s old reliable, around since the very beginning of iOS itself. Great for developing complex interfaces with advanced functionality, UIKit is a great solution for apps needing bespoke experiences or interfaces. There is also a widespread ecosystem of third-party libraries and UI components to draw from.

But there are some drawbacks. Many developers have cited a steep learning curve in getting started with the framework. Because of this inherent difficulty, it can easily cause issues to leak into production. There’s also a time-intensive development process that isn’t quite optimized for the constant release of new devices every year.

SwiftUI 

So how does SwiftUI measure up? For starters, SwiftUI uses a much more straightforward and declarative syntax. Gone are the days of UIKit’s imperative platform approach – SwiftUI simplifies and localizes more of the logic in one place with its declarative framework. There’s also Live Preview, which allows developers to test and see resulting views in real-time. And there’s cross-platform support, allowing shared frameworks to be used.

But no platform is perfect. SwiftUI does not support earlier iOS versions, with iOS 13 as its earliest supported version. It also requires you to conform to system standards, meaning there is not as much room for customization as there is in UIKit. Additionally, more complex UI configurations may allow performance issues to slip into production.

Considerations: Should I Migrate to SwiftUI?

There are three areas to consider when deciding whether to migrate to Swift UI: your customers, team, and product.

Know Your Customers

At the end of the day, your key metric is customer experience. To know whether to migrate to SwiftUI, you need to consider if it’s in the best interest of your customers. What percentage of users on are on iOS 13 or prior? What percentage of users’ devices support iOS 13 and above? Analyzing this data will allow you to see if migration makes sense for your users.

Know Your Team

It is critical to make sure your team is comfortable in your chosen production environment. Given the complexity of UIKit and its steep learning curve, would it be better to migrate to a simpler framework like SwiftUI? Are you hiring soon? How much SwiftUI experience do you have on your team? Asking these questions will provide insights into your team’s preferences and allow you to set them up for success.

Know Your Product(s)

Having a fancy new framework isn’t great if it doesn’t play well with your product and how it’s set up. If you’ve already set up very customized interfaces in UIKit, they may be missing from SwiftUI. You also need to consider how other teams at your company may depend on the way you have built your application.

Options for Migrating to SwiftUI

Migrating is no simple feat – you and your team need to be on the same page regarding your strategy. Some companies may opt to mix and match the best-fit features from both SwiftUI and UIKit, but that can cause more issues down the road. A full migration is more time-intensive but may save resources later. Let’s look at the most common integration paths.

Top-Down Migration

This migration option is effectively a rewrite or mandate to migrate everything over to SwiftUI. This allows you to utilize consistent patterns and helps to avoid migrating legacy code. Everyone has worked at a place where there’s some old code that somebody wrote a long time ago that nobody understands anymore – a top-down migration forces developers to reimagine and modernize that code. This works best on simple applications or relatively new applications.

On the downside, a full top-down migration is a large upfront investment of time and resources. Depending on the size of your application, it could be hundreds or thousands of hours of developer time. You need to carefully plan your team’s approach to avoid duplicating work and ensure the end-user experience isn’t compromised.

Bottoms-Up Migration 

The top case for a bottoms-up migration is it significantly limits your risk. By starting with new modules and migrating simple interfaces first, you can work out the kinks before committing to larger, more complex elements. This is less disruptive to your team, too. This approach works best for most apps with a wide customer base that release regularly and require very high stability.

However, a bottoms-up migration leaves room for error in lack of standardization and could create a need for bridging your code.

Don’t Migrate

Your team doesn’t always have to follow the trend. Small teams may have no desire or business case to migrate from UIKit to SwiftUI. Any applications with a significant portion of users on iOS 13 or prior have little reason to make the jump. Also, if your application has limited releases or feature changes, the case for migration is relatively weak.

Conclusion 

At the end of the day, no two companies, no two teams, and no two apps are the same. There is no one-size-fits-all approach to conducting a large migration. Moving your application from UIKit to SwiftUI is no easy feat, and you’ll need to make sure such a large undertaking is in the best interest of your product and your team.

Want to learn more about migrating from UIKit to SwiftUI? Check out this webinar to hear from our experts.

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