SwiftUI vs. UIKit: Which iOS App Development Framework is Better for Your iOS App?

Choosing the appropriate framework for iOS development, SwiftUI vs. UIkit comparison automatically pops up. The parent-child analogy suits these two Apple frameworks. 

UIkit is like the parent who is more mature with a plethora of features. SwiftUI is the successor, a recently launched work in progress, with many updates and features and holding the future baton of Apple. 

iOS development got a new definition with the launch of Swift language. Before that, Objective-C was the language for UIkit, and now Swift is the language used in SwiftUI. This blog is an overview of their features, similarities, and differences to understand the frameworks and aid you in deciding to pick the perfect choice for your next project.

SwiftUI vs. UIkit: A History

Apple ecosystem developers have yet to be overrun with choices. Developers spent considerable time using only Objective-C and some C++. They have had the pleasure of witnessing language change and innovation since the release of Swift. However, they were limited to using UIkit for UI development.

The basis for creating views and the user interface for iPhones has been UIkit since iPhone OS 2. UIKit has been a robust and adaptable platform for UI development for more than 11 years. The UIkit community has had ample opportunity to accumulate a plethora of knowledge as a result. 

UIkit is undoubtedly the parent having more experience and more APIs to support, but the younger one, SwiftUI, is keeping pace with the time going around it. To understand SwiftUI, you’ll have to learn UIkit.

What is SwiftUI?

A relatively recent addition to the Apple environment is SwiftUI. It was initially made available in 2019, along with iOS SDK version 13. However, SwiftUI has developed to the point that it’s now a practical choice for many app developers, mainly when aiming for iOS 14+ or even 15+. However, a particular set of restrictions with SwiftUI on iOS 13 has slowed iOS app developers’ uptake.

Unlike UIKit, SwiftUI is a UI framework with a more reactive approach to UI development. Using UIKit, setting up your views is quite straightforward: Window and user interface (UI) changes require calculating and updating sizes or adding and removing views from the view hierarchy.

Conversely, SwiftUI focuses more on specifying what you want to see on the screen. Future versions of SwiftUI might compute all the differences and change the representation automatically presented to the end user when the screen’s content needs to change. You have complete control over what and where happens on-screen. Even so, changes to the UI’s underlying state lead to the actual rendering. The way UIKit operates is quite the reverse; as a developer, you must actively update the entire UI to reflect the altered state.

When comparing SwiftUI Vs. UIkit, SwiftUI makes extensive use of Swift language features. This is essential because, in order to construct SwiftUI as it is today, Apple first had to incorporate particular characteristics within the Swift language. Apple first publicly released Swift in 2014, and multiple updates have been made since its launch. While some of these modifications were rather insignificant, others had a more significant impact. 

Advantages of SwiftUI

• SwiftUI offers UI development that is quicker and easier, which is its main benefit.
• Since SwiftUI has a declarative syntax, developers may control how the UI functions and appears without going through a series of steps.
• An added benefit of SwiftUI is its interaction with the Swift framework. For developers who are familiar with Swift, getting started is simple.
• SwiftUI’s cross-platform compatibility is yet another significant benefit. It makes it possible for developers to quickly and affordably construct user interfaces for various Apple devices.
• Compared to UIKit, which requires developers to create each transition and animation in the code, SwiftUI provides more of each.

Drawbacks of SwiftUI

• SwiftUI’s restricted compatibility with earlier iOS versions is one of its drawbacks.
• To support iOS versions before iOS 13, developers might need an alternative.
• It’s important to remember that between UIkit Vs. SwiftUI, SwiftUI may have modification restrictions compared to UIKit.
•  The declarative syntax reduces developers’ control over the user interface appearance and functionality. It might not be advantageous for programs that demand a highly customized user interface.
• SwiftUI can potentially have performance concerns, especially with more intricate UI designs.

What is UIKit?

With the help of the UIKit framework, you can create user interfaces (UI) that can manage user, system, and app interactions while handling touch events and inputs. UIKit is a component of CocoaTouch, which was made accessible with the initial release of iOS, formerly known as iPhoneOS, in 2008 as part of the iOS SDK.

A UIKit app’s structure is depicted in Figure in a reasonably typical fashion. The model objects that represent the data structures in your program are the ones you supply. UIKit provides the majority of view objects, but you can also create custom views for your data as necessary. Your view controllers and app delegate object coordinate the data transfer between your data objects and the UIKit views.

UIKit was created secretly for the first two iOS releases before then. Since it was made available to the public in 2008, UIKit has not shown any symptoms of being abandoned by Apple. When developing iOS apps, UIKit offers the most comprehensive and feature-rich developer experience.

UIKit was created and published using the Objective-C programming language. Even today, when programming for iOS development, you frequently encounter Objective-C code.  

Objective-C was created on top of the C language to enable object-oriented programming. Before Apple’s revival and release of the iPhone, Objective-C had a significant impact.

Advantages of UIKit

As a mature framework utilized from the inception of iOS development, UIKit has a significant benefit.

• The framework has a sizable and vibrant developer community knowledgeable about UIKit.
• Due to its imperative syntax, UIKit provides more customization options. These choices offer programmers more control over the UI’s appearance.
• High-performance visuals are provided by UIKit, which makes it the best choice for apps that need a responsive and fluid UI.
• A key benefit of UIKit is its highly optimized graphics capabilities. As a result, it is appropriate for apps that use animation, video, or other potent graphics in iOS development or custom iOS app development.

Drawbacks of UIKit

• The steep learning curve of UIKit is a severe flaw. Since programmers must define a series of procedural steps in order to generate the UI, the learning becomes a bit complex.
• It’s important to remember that SwiftUI is well-known for its declarative syntax and built-in choices when comparing SwiftUI Vs. UIKit. Compared to UIKit, it is easier to understand thanks to these characteristics. In contrast to UIKit, this minimalist approach may give developers fewer customization options.
• The creation of UIKit can be time taking. Particularly for a fully customized UI, developers must list down several steps.
• For novice developers, using UIKit can be tricky, which increases the likelihood of blunders and difficult-to-locate faults.
• It’s crucial to remember that UIKit only supports iOS apps and is not platform-neutral.

SwiftUI Vs. UIKit

UIkit is an imperative framework, i.e., in this framework programmer needs to give commands as to how and what type of layout or interface is necessary. It is a verbose platform, hence requiring more coding to develop interfaces. UIkit has been present since the launch of iOS2. 

Swift UI is a declarative framework easing the developing task with its highly evolved and intuitive interface. Developers utilize the “declarative syntax” to create interactive interfaces which are less verbose. SwiftUI came into existence after the evolution of UIkit. 2019 is the year when SwiftUI was launched with iOS13. 

Declare your project’s user interface and behavior across all platforms using SwiftUI.

Use UIKit to build and manage a graphical, event-driven user interface for your applications for iPhones or Apple TVs. Now let’s dive into the details of some of the features to understand the comparison between UIkit Vs. SwiftUI:- 

Approachability

 Evolution becomes the cause for advancement.

Sometimes evolution simplifies things, and that is the case with SwiftUI. Determining the problems in UIkit and resolving them made SwiftUI a very approachable framework compared to UIkit. A simple example of the “Hello World” interface for Swift and UIkit proves this. 

This is a window for SwiftUI.

And this is the window for UIkit

Development Speed

Many iOS developers believe SwiftUI is now the quickest way to implement in-app features. You may find some comparisons between creating the same functionality in SwiftUI and UIKit online. It is evident from these comparisons that SwiftUI generally takes a lot less code to produce the same outcomes as UIKit.

But there is a catch: UIKit has far more features than SwiftUI. Every time UIKit offers a capability that SwiftUI doesn’t, you typically need to use the UIViewRepresentable protocol to translate that functionality into SwiftUI.

When using SwiftUI, your data, and the view hierarchy displaying your data are much more loosely related, which is one of its main advantages. This allows you more freedom when reusing the model and viewing the hierarchy logic already included in SwiftUI. This is yet another of SwiftUI’s key advantages. Correctly implementing SwiftUI encourages significantly more apparent abstractions in your code.

Additionally, SwiftUI’s Live Preview functionality considerably speeds up development when it’s functional. SwiftUI’s much longer learning curve while you try to understand how SwiftUI wants to “do user interfaces” is a disadvantage. Compared to UIKit, the pool of engineering talent familiar with SwiftUI is still significantly smaller. 

Performance

Taking developer performance and app performance into account for this aspect.

Regarding the end result, we haven’t seen any observable differences between the performance of the two frameworks. Rendering isn’t any faster because SwiftUI uses UIkit and AppKit in the background.

Nevertheless, when it comes to development build time, SwiftUI often outperforms UIkit. This is because there are no expensive memory allocations. After all, the hierarchy of views is stored in value-type structs on the stack. And in some circumstances, that means improved performance.

Additionally, quickly reviewing your changes while you work dramatically increases productivity.

SwiftUI wins in this case.

Support

We can see UIkit has come a long way from iOS2-iOS12 and still is in use. This maturity contributes to its many features making it more supportive than Swift as it is younger comparatively.

When comparing UIkit Vs. SwiftUI, there is a lot more UIKit content available than there is for SwiftUI. However, this is gradually changing as more people begin adopting SwiftUI. The quantity of UIKit-based codebases that are now in existence must be considered. Because of supported version constraints lower than iOS 13, many codebases simply cannot embrace SwiftUI. As a result, UIKit will continue to receive the most ongoing, practical development work for the foreseeable future.

SwiftUI claims to function on every Apple product. Your SwiftUI views should support any screen size. The implication here, though, is not that you can write once and run anywhere.

Most Apple ecosystem software can be transferred using the UI programming model; however, you need to test SwiftUI code built for an iPhone in its new environment when moving it to macOS.

This does make it possible to build cross-platform components and drastically reduce the amount of platform-specific code.

Testing

We found it exceptionally aggravating since there was so little information on testing SwiftUI elements properly and simulating user behavior. It’s even been off-putting at times. Of course, that doesn’t mean we haven’t come up with our own answers despite that. And they frequently seem to produce positive outcomes.

But if you’re thinking about using SwiftUI, you should be aware that this is part of the platform that has developed the least quickly. Applications based on UIKit and SwiftUI can both construct UI tests using XCTest. 

Conclusion

The recent WWDC 23 has changed the way UIkit is seen. Features like spatial computing for creating astronomy apps, enabling animate symbols in the app, and other features are taking this framework to the next level. The UIkit trait system is a powerful enhancement to UIkit. You can alter the traits to add your own information to the UItraitCollection. It is making it easier to adopt APIs to improve flexibility. If you find it difficult to work with new upgrades, hire iOS developers who can easily implement the newest features and transform your application into a more trendy version.

On the other hand, SwiftUI is also power packed with the spatial computing feature incorporating the visionOS and making the user experience more lucid. Simplifying your data models with the Observation feature. One indispensable feature is the Swift macro to reduce the boilerplate in the codebase and adopt complex features easily.

Both frameworks are apt as you start working on them and experience their functionalities. Although UIkit was becoming a bit old, Apple aimed to revive it with multiple features. 

Building accessible apps has become more convenient and easy with UIkit and SwiftUI. Interoperability is again one of the good features, making it hard to choose any of them. 

A good decision depends on your project requirements. And you can take expert help from Moon Technolabs for further queries in your iOS development journey. A standard approach for custom mobile application development is taken to build your apps. Developers from Moon Technolabs keep in mind the guidelines given by Apple and suggest you the best option. Our help starts at the beginning of your journey, from choosing the proper framework to submitting your application to the App Store.