SwiftUI vs UIKit: Which Framework Should You Use?

iOS 13 introduced us to a new and innovative framework- SwiftUI. This framework is introduced as a better alternative to UIKit due to its simplicity and speed of coding. It allows the iOS development team to design and develop user interfaces declaratively with lesser code than UIKit (for applications possessing the same complexity). SwiftUI is also entirely software-based, unlike UIKit, which is commonly used in conjunction with storyboards. It has very clear syntax and uses Automatic Preview to quickly view a SwiftUI project.

However, the objective of both SwiftUI and UIKit is the same- to allow iOS developers to create powerful applications. The iOS development community often debates the two. If you are also planning to build an iOS app and are confused as to which framework should you opt for, this SwiftUI vs UIKit guide will help you in your decision. Both UIKit and SwiftUI offer a plethora of benefits, while at the same time, each comprises a few drawbacks as well. Let’s understand both these frameworks.

UIKit

UIKit or User Interface Kit has been the ultimate framework to develop user interfaces for iOS applications. It’s a part of CocoaTouch and has been the backbone of UI development in iOS for over a decade. UIKit possesses the ability to build user interfaces even without a strong programming background. That’s because UIKit introduced us to storyboards that help create interfaces using the drag-and-drop functionality. This, in turn, makes app development simplified and quite effortless. Additionally, it saves developers time due to storyboards doubling as a preview.

UIKit provides diverse objects, such as UIView and its subclasses, which can be used to create iOS apps. These objects allow for the display and interaction of content within the application. Apps built with UIKit generally make use of the MVC pattern.

Being a well-established framework, UIKit has plenty of resources available to get your queries addressed.

UIKit apps can be developed in a few different ways, such as-

1. Using Interface Builder for UI design without coding. Interface Builder is integrated into Xcode and lets you edit .storyboard and .xib files, both of which use XML to describe layouts.

2. A code-focused approach with defined views and layout constraints.

3. A blend of both.

Drawbacks

Speaking of UIKit drawbacks, it is relatively difficult to build user interfaces programmatically, i.e. without storyboards in UIKit. Moreover, it is an imperative framework which means that one has to write code to specify the steps that the computer must take to accomplish the task.

Since UIKit is an older framework, it is very likely that it might stop receiving support from Apple in the future.

SwiftUI

SwiftUI was first released in 2019 in iOS 13 and has already proved to be a game-changer in iOS development in a very short period. In comparison to UIKit, it’s a more powerful library and is very easy to learn- has a very clean and easy-to-understand syntax. But what sets SwiftUI apart from its counterpart is its declarative approach. While UIKit is an imperative framework, SwiftUI is a declarative framework, which simply means that you declare the task you want to accomplish.

SwiftUI can also be combined with UIKit with the help of UIHostingController. It also offers Live preview which is a great way to see the outcomes of code execution in real-time without having to build. Also, with SwiftUI, your application won’t crash if you forget to update the @IBOutlet association with the variable.

Simply put, building apps with SwiftUI is more streamlined than building apps with UIKit. It allows developing applications across all Apple platforms with little coding involvement.

1. Xcode shows the visual editor alongside any file that involves a SwiftUI view, thereby showing a live representation of the view you are building. You can still interactively design on the canvas, just like in Interface Builder.

2. .storyboard and .xib files are not used in SwiftUI. The Swift code describes the layout itself rather than the opaque XML files.

Since SwiftUI is a successor of UIKit, it has addressed certain challenges that developers earlier faced with the latter. It provides them with much more features that were unavailable in UIKit. And the framework will continue to evolve as the Apple team shifts its focus away from UIKit to SwiftUI.

Drawbacks

Although the benefits are plenty, there are a few drawbacks associated with SwiftUI as well. With SwiftUI, the norm is building user interfaces programmatically, so the focus remains more on that aspect and less on storyboards. This isn’t always a drawback but can be a benefit as well depending on the developer’s preferences.

Another drawback of SwiftUI is that it only supports versions ≥ iOS 13 and Xcode 11. So by opting for it, you abandon users whose devices are still running on older iOS versions. However, the usage of SwiftUI would increase further in the coming years as more and more users would be on iOS 13.

The third drawback is that SwiftUI doesn’t allow examining the view hierarchy in Xcode Previews. 

Though SwiftUI is now quickly becoming the superior framework for building iOS applications, being relatively new, quite a few developers are still not very familiar with it. So it can get a bit difficult for them to build complex SwiftUI applications. There isn’t much data on Stack Overflow which means you won’t get much assistance while resolving complicated issues.

Final Thoughts

Choosing a framework between SwiftUI and UIKit can depend on the type of developer using them. A visual-oriented developer would likely prefer UIKit whereas a program-oriented developer would have a preference for SwiftUI.

It can also depend on the type of project that you are working on. Both UIKit and SwiftUI have their own use cases so you’ll have to assess which one of the two suits the project most. However, today, if one has to choose between these two frameworks, most iOS developers would go with the successor as it provides more powerful code elements, suits the current needs, and is better optimized for newer devices.