3.0.0 — Xcode 27 / iOS 18

The Xcode 27 release. The minimum deployment target is now iOS 18.0 and the package needs a Swift 6.2 compiler (Xcode 26.0 or later). This is a breaking upgrade from 2.1.0 — see Breaking Changes below and Migration from 2.x to 3.0 in the README.

Most of this release is performance work, and none of it changes an observable result. Each rewrite is pinned by a differential test that runs the new code and a frozen copy of the 2.1.0 algorithm it replaces on the same inputs and requires identical output, and each differential test was checked by breaking the new code on purpose (mutation checks) to confirm that it turns red.

Breaking Changes

Change	Migration
Minimum deployment target raised from iOS 15.0 to iOS 18.0	The library now uses Mutex and Atomic from the Synchronization module, which first shipped in iOS 18
A Swift 6.2 compiler (Xcode 26.0+) is required	Package.swift declares swift-tools-version: 6.2. CocoaPods has no equivalent check, so Sources/SwiftyGlobal.swift turns an older compiler into one readable #error instead of a wall of syntax errors
ImageCachePool.defalut and SwiftyThreadPool.defalut removed	Use .default. Both had been deprecated, with a rename fix-it, since 2.0
ClosureVoidWrapper removed	The library never used it. Use ClosureWrapper
SwiftyAppearance's initializer no longer takes kWindowHeight, kTextHeight or dynamicAnimatorActive	Delete those arguments. None of them has had any effect since 2.0
SwiftyLabel copies attributedText, paragraphStyle and shadow when you assign them, as UILabel does	Mutating the object you assigned no longer changes the label; assign it again. 2.x re-read these objects on every draw, so in-place changes used to show up at the next redraw. With the cached text storage (see Changed) such changes would go half stale — the text stuck, the layout lagging — so 3.0 adopts UILabel's copy semantics instead

Fixed

• The example app no longer crashes on launch on iOS 27. iOS 27 traps any app built with the iOS 27 SDK that has not adopted the UIScene life cycle (_UIApplicationEvaluateRuntimeIssueForNoSceneLifecycleAdoption), and iOSExample still had its 2017 AppDelegate + window setup. Five of the six UI tests failed and the app-hosted iOSExampleTests could not run at all; CI stayed green only because it builds the example without launching it. The app now has a SceneDelegate and a scene manifest, and the five application life-cycle methods that iOS 26 deprecated are gone from its AppDelegate.

Changed

• Promise keeps its state behind a Mutex. 2.x guarded every critical section with sync on a serial DispatchQueue. An uncontended Mutex lock is a single atomic operation with the lock stored inline. The critical sections are exactly the ones 2.1 had — none merged, none split — because the correctness arguments in registerValueWaiter and markError depend on which steps share one. The two single-flag helpers became lock-free: the "did this block run" flag is an Atomic<Bool> written with release and read with acquire ordering, and the "resume the continuation once" guard is one compare-exchange.
• SwiftyThreadPool and ImageCachePool use Mutex instead of NSLock. No Objective-C message send per lock and unlock. Each memory-warning observer token now lives inside the locked state as well.
• Promise, SwiftyThreadPool and ImageCachePool are now checked Sendable instead of @unchecked Sendable, so the compiler verifies their thread safety. ThreadPerform gained a Sendable conformance along the way. All of this is source compatible.
• ImageCachePool evicts in O(1) per entry. 2.x sorted every entry by its access counter whenever the cache went over capacity — inside the lock, and on every add once the cache was full. The cache is now a dictionary plus a doubly linked list whose nodes live in one contiguous array and link to each other by index, so list updates cost no reference counting and freed slots are reused. The eviction rule is unchanged to the letter: entries are removed oldest first, the check comes after each removal (so going over capacity always evicts at least one entry), and the newest entry is evicted too if that is what it takes.
• UIImage.colors() counts colours in one cheap pass and no longer sorts them all. 2.x counted the pixels of the 250-pixel-wide downsample in a [UInt32: Int] dictionary, then created a UIColor for every distinct colour in the image, desaturated it, read its components and sorted all of them — tens of thousands of colours in a photo, although the selection loop usually stops after a few dozen. Pixels are now counted in a single pass into an open-addressing table hashed with one multiplication, and runs of identical neighbouring pixels are added in one step, so flat artwork costs a few lookups per row. The candidates then come out of a max-heap in the original order (most frequent first, ties broken by colour value); each one becomes a UIColor only when the loop reaches it, and the loop still stops as soon as it has all four colours. Both the callback and the async variant get this.
• SwiftyLabel keeps one NSTextStorage for its whole lifetime. 2.x copied the attributed text, filled in the default attributes, built a new text storage and re-attached the layout manager on every draw and every sizeThatFits — and intrinsicContentSize goes through sizeThatFits, which Auto Layout calls several times per pass — so glyphs were generated from scratch every time. The storage is now rebuilt only after the text or one of its attributes changes; a new container size only invalidates layout.
• SwiftyToast no longer animates while it holds. The 2.5-second hold between fading in and fading out used to be an animation of alpha from 1 to 1.0001: nothing visible changed, but Core Animation composited the layer on every frame for the whole hold and the render loop could never go idle. The hold is now a Task.sleep. Two UI tests that wait for the app to become idle got faster as a side effect.
• Promise.value() and UIImage.colors() are explicitly nonisolated(nonsending). They register on the caller's actor instead of hopping to the global concurrent executor first. Writing it on the declaration keeps the behaviour the same whatever build settings the library is compiled with.
• Smaller allocations removed: UIColor.hex(_:) parses the string's UTF-8 bytes directly instead of building intermediate strings, with exactly the same accept and reject rules; SwiftyGlobal.keyWindow walks the connected scenes without building an intermediate array; SwiftyGlobal.modelName decodes the uname bytes instead of reflecting over a 256-element tuple with Mirror.

Tooling

• Package.swift: swift-tools-version: 6.2, iOS 18, an explicit Swift 6 language mode, and five upcoming features turned on for both targets — NonisolatedNonsendingByDefault, InferIsolatedConformances and MemberImportVisibility (Xcode 27's defaults for new targets) plus ExistentialAny and InternalImportsByDefault. All five are Swift 7 language mode defaults. As a result, sources that expose UIKit or Foundation types publicly now say public import.
• SwiftyUI.podspec turns on the same five features through pod_target_xcconfig, and the Xcode project's framework target does the same, so CocoaPods, Swift Package Manager and the example project compile the same source the same way.
• The Xcode project takes Xcode 27's recommended settings: deployment target 18.0 on every target (which also silences five XCTest linker warnings), the template's warning and language-standard settings, and SWIFT_COMPILATION_MODE = wholemodule for Release in place of the pre-Xcode 10 -Owholemodule optimization level. The UI test class is main-actor isolated, which clears 121 isolation warnings from Xcode 27's newly annotated XCUIAutomation.
• CI: actions/checkout v5 → v7, and the Xcode floor check moves from 16 to 26. Jobs stay on macos-latest, which ships Xcode 26.6; Xcode 27 is only available under GitHub's xcode-27 preview label.
• Scripts/check-readme.sh type-checks the README examples against iOS 18.