Technologies / Swift
Swift app development for iPhone, iPad and Apple Watch
Swift app development is how we build native Apple apps: one modern, type-safe language for the app logic, with SwiftUI or UIKit for the screens. This page is for founders and CTOs deciding whether Swift is the right foundation, not a tutorial. It covers what Swift 6 changed, how it lives alongside older Objective-C code, and what the choice means for hiring and maintenance over the next five years.
Swift is Apple’s preferred language on iPhone, iPad, Mac, Apple Watch, Apple TV and Vision Pro, and Apple’s newer frameworks are designed around it; SwiftUI, launched at WWDC 2019, exists only in Swift. For a buyer, the language decides how many bugs the compiler catches before users do, how easily the next developer can change the code, and how fast you can adopt new Apple features after each June WWDC.
If you already know you want a native iOS app, our iOS app development services page covers scope, process and App Review. The notes here explain why the language underneath matters to your budget.
- Swift 6 language mode on new code
- Objective-C interop for legacy apps
- Xcode 26 and iOS 26 SDK builds
- Code in your own repository
Swift 6 and data-race safety: the change that matters most
Swift 6 was released on 17 September 2024. Its headline feature is an opt-in Swift 6 language mode that turns potential data races into compile-time errors, according to the Swift 6 announcement. The same release brought Swift Testing, a newer testing library, and a fully static Linux SDK.
A data race happens when two threads touch the same memory at once and one of them writes. In an app that shows up as bugs nobody can reproduce: stale lists, rare crashes, a payment screen that double-submits.
With structured concurrency (async/await, actors, Sendable types) and the Swift 6 language mode switched on, the compiler refuses to build code that could race. That moves the cost from production firefighting to the moment the code is written.
What we do about it on your project
New apps start in the Swift 6 language mode. Existing apps move module by module: we turn on strict concurrency checking as warnings first, fix the hot spots (shared caches, singletons, callback-based networking), then flip each module to Swift 6. Converting a large app in one sprint is a common failure: hundreds of errors and a stalled release train.
When we choose Swift, and when we do not
We recommend Swift app development when the app lives close to the operating system or the Apple audience is the business. Widgets, Live Activities, HealthKit, Apple Pay, background location, Apple Watch companions and on-device ML with Core ML all work best, and arrive soonest, in native Swift.
We do not recommend Swift-only when you need Android at launch on a tight budget and your screens are mostly standard forms and lists. One shared codebase in Flutter or React Native is usually cheaper there; Clutch’s app cost guide (updated September 2026) says separate native iOS and Android apps roughly double the cost of one cross-platform build. See our native vs cross-platform guide.
Choose Swift if
- Your first users are on iPhone or iPad
- You need Watch, widgets, HealthKit or Apple Pay deep integration
- Performance or battery life is a selling point
- You are extending an existing Objective-C or Swift app
- You plan to hire in-house iOS engineers later
What we build with Swift
Swift covers the whole Apple stack. These are the project types we most often scope.
SwiftUI apps
New consumer and B2B apps with SwiftUI screens, Swift concurrency for networking, and Swift Package Manager modules.
iPhone apps
Commerce, booking, fintech and health apps built for one-handed use, Dynamic Type and Dark Mode.
Objective-C modernisation
Incremental rewrites of older apps: new screens in Swift, old modules wrapped, nothing switched off at once.
Apple Watch and widgets
watchOS companions, home-screen widgets and Live Activities, each with its own entitlement and review notes.
On-device AI
Core ML features that run on the device so personal data stays on the phone.
Objective-C interop: modernising without a rewrite
Many apps that reach us predate mature Swift. A full rewrite is rarely right: it freezes the roadmap and reintroduces bugs the old code had already fixed.
Swift and Objective-C can live in the same target. A bridging header exposes Objective-C classes to Swift, and Swift classes marked for Objective-C can be called from the old code. That lets us write every new feature in Swift, wrap legacy modules behind clean interfaces, and retire Objective-C file by file as features are touched anyway.
The catch is that interop has seams. Objective-C has no optionals, so we add nullability annotations to old headers before Swift code depends on them; otherwise the compiler guesses and crashes return.
How Swift fits the rest of your stack
The Swift app is the client. Behind it sits an API and admin tooling, which we usually build in Node.js, Laravel or Firebase depending on scale and team. Our mobile app backend development page explains those choices. If you also need Android, the native partner is Kotlin; the two codebases share an API contract, design system and analytics plan rather than code.
Delivery tooling is standard Apple: Xcode, Swift Package Manager, XCTest and Swift Testing, TestFlight for every sprint build, and CI on GitHub Actions or Codemagic with Fastlane. Since 28 April 2026, uploads must be built with Xcode 26 and the iOS 26 SDK family, per Apple’s upload requirements, so CI pins the current Xcode and we flag any SDK that blocks an upgrade early.
Not sure Swift is right for your app?
Send us your feature list. Within one business day you get our recommendation on Swift, cross-platform or a mix, with the reasons and the trade-offs in plain English.
Swift compared with the alternatives
How Swift app development compares with the other ways to put an app on an iPhone.
| Option | Best for | Trade-off |
|---|---|---|
| Swift + SwiftUI | New Apple-first apps, deep OS integration, long-lived products | Android needs a second codebase |
| Swift + UIKit | Complex text, camera and legacy screens; extending older apps | More code per screen than SwiftUI |
| Flutter (Dart) | iOS and Android from one codebase with custom UI | Platform features need native plugins |
| React Native (JS/TS) | Teams with React web skills, shared logic with web | Native modules for advanced platform work |
| Kotlin Multiplatform | Sharing logic with an Android Kotlin app | iOS team consumes Kotlin-generated code |
Hiring and maintenance implications
Swift is the language every current iOS engineer learns, so hiring is straightforward and the code you own stays transferable. If you later bring development in-house, a clean Swift codebase is the easiest handover in the Apple world. You can also hire iOS developers from us on a dedicated or staff-augmentation basis, with a two-week trial.
Maintenance follows Apple’s yearly cycle: betas after WWDC in June, public release in September, and minimum Xcode and SDK requirements for uploads that Apple raises with notice (the latest took effect on 28 April 2026). Budget for a yearly Xcode, SDK and Swift upgrade. Our app maintenance and support plans cover that cadence.
Code-quality practices on our Swift projects
What you can check in your own repository at any sprint review.
- Swift 6 language mode or strict concurrency checking enabled per module
- Feature modules as Swift packages with clear public interfaces
- SwiftLint and SwiftFormat run in CI; warnings treated as work, not noise
- Unit tests in XCTest or Swift Testing for view models and business rules
- No force unwraps outside tests; nullability annotated on any Objective-C headers
- Crash reporting through Crashlytics or Sentry with symbol upload in CI
- Pull requests reviewed by a second iOS engineer before merge
Swift app development: frequently asked questions
Is Swift better than Objective-C for a new app?
Yes, for any new app. Swift is Apple’s preferred language, SwiftUI only exists in Swift, and Apple’s newer APIs are designed around it. Objective-C is still supported and we maintain it in older apps, but starting a new project in it would narrow your hiring pool and slow adoption of new platform features. Use Objective-C only where existing code already lives.
Do we need to rewrite our Objective-C app in Swift?
Usually not. Swift and Objective-C run side by side in one project, so we write new features in Swift and convert old modules when they are touched for other reasons. A full rewrite only makes sense when the old code blocks critical work, such as a Swift 6 or SDK upgrade, and even then we do it module by module so releases continue.
What does Swift 6 change for our existing app?
The Swift 6 language mode turns potential data races into compile errors. Older code that shares mutable state across threads will need fixes before that mode is switched on. Most teams enable strict concurrency warnings first, fix the riskiest areas, then move module by module. The work pays off in fewer intermittent crashes that are hard to reproduce.
Can Swift be used for Android?
Not as a mainstream option for production Android apps today. For iOS and Android together you either build two native apps, Swift and Kotlin, or use a cross-platform framework such as Flutter or React Native. Kotlin Multiplatform is another route that shares business logic written in Kotlin with an iOS app. We help you pick based on budget, features and team.
Should we use SwiftUI or UIKit?
New screens default to SwiftUI because it is faster to build and preview and is Apple’s direction. UIKit still earns its place for complex text editing, some camera flows and large legacy apps. Mixing the two is fully supported.
How do you keep a Swift app working after each iOS release?
We test against Apple betas from June, fix deprecations before the September public release, and plan the Xcode and SDK upgrade before Apple’s next upload requirement takes effect. Since 28 April 2026, uploads must use Xcode 26 and the iOS 26 SDK. A maintenance plan makes this routine work rather than an emergency the week a release is due.
Build your iOS app on a Swift foundation that lasts
Book a 30-minute scoping call. We will look at your features, any existing code, and the Apple integrations you need, and recommend a Swift setup you can maintain for years.