--- name: swiftui-gestures description: "Implement, review, or improve SwiftUI gesture handling. Use when adding tap, long press, drag, magnify, or rotate gestures, composing gestures with simultaneously/sequenced/exclusively, managing transient state with @GestureState, resolving parent/child gesture conflicts with highPriorityGesture or simultaneousGesture, building custom Gesture protocol conformances, or migrating from deprecated MagnificationGesture to MagnifyGesture or using the newer RotateGesture." --- # SwiftUI Gestures (iOS 26+) Review, write, and fix SwiftUI gesture interactions. Apply modern gesture APIs with correct composition, state management, and conflict resolution using Swift 6.3 patterns. ## Contents - [Gesture Overview](#gesture-overview) - [TapGesture](#tapgesture) - [LongPressGesture](#longpressgesture) - [DragGesture](#draggesture) - [MagnifyGesture (iOS 17+)](#magnifygesture-ios-17) - [RotateGesture (iOS 17+)](#rotategesture-ios-17) - [Gesture Composition](#gesture-composition) - [@GestureState](#gesturestate) - [Adding Gestures to Views](#adding-gestures-to-views) - [Custom Gesture Protocol](#custom-gesture-protocol) - [Common Mistakes](#common-mistakes) - [Review Checklist](#review-checklist) - [References](#references) ## Gesture Overview | Gesture | Type | Value | Since | |---|---|---|---| | `TapGesture` | Discrete | `Void` | iOS 13 | | `LongPressGesture` | Discrete | `Bool` | iOS 13 | | `DragGesture` | Continuous | `DragGesture.Value` | iOS 13 | | `MagnifyGesture` | Continuous | `MagnifyGesture.Value` | iOS 17 | | `RotateGesture` | Continuous | `RotateGesture.Value` | iOS 17 | | `SpatialTapGesture` | Discrete | `SpatialTapGesture.Value` | iOS 16 | **Discrete** gestures fire once (`.onEnded`). **Continuous** gestures stream updates (`.onChanged`, `.onEnded`, `.updating`). ## TapGesture Recognizes one or more taps. Use the `count` parameter for multi-tap. ```swift // Single, double, and triple tap TapGesture() .onEnded { tapped.toggle() } TapGesture(count: 2) .onEnded { handleDoubleTap() } TapGesture(count: 3) .onEnded { handleTripleTap() } // Shorthand modifier Text("Tap me").onTapGesture(count: 2) { handleDoubleTap() } ``` ## LongPressGesture Succeeds after the user holds for `minimumDuration`. Fails if finger moves beyond `maximumDistance`. ```swift // Basic long press (0.5s default) LongPressGesture() .onEnded { _ in showMenu = true } // Custom duration and distance tolerance LongPressGesture(minimumDuration: 1.0, maximumDistance: 10) .onEnded { _ in triggerHaptic() } ``` With visual feedback via `@GestureState` + `.updating()`: ```swift @GestureState private var isPressing = false Circle() .fill(isPressing ? .red : .blue) .scaleEffect(isPressing ? 1.2 : 1.0) .gesture( LongPressGesture(minimumDuration: 0.8) .updating($isPressing) { current, state, _ in state = current } .onEnded { _ in completedLongPress = true } ) ``` Shorthand: `.onLongPressGesture(minimumDuration:perform:onPressingChanged:)`. ## DragGesture Tracks finger movement. `Value` provides `startLocation`, `location`, `translation`, `velocity`, and `predictedEndTranslation`. ```swift @State private var offset = CGSize.zero RoundedRectangle(cornerRadius: 16) .fill(.blue) .frame(width: 100, height: 100) .offset(offset) .gesture( DragGesture() .onChanged { value in offset = value.translation } .onEnded { _ in withAnimation(.spring) { offset = .zero } } ) ``` Configure minimum distance and coordinate space: ```swift DragGesture(minimumDistance: 20, coordinateSpace: .global) ``` ## MagnifyGesture (iOS 17+) Replaces the deprecated `MagnificationGesture`. Tracks pinch-to-zoom scale. ```swift @GestureState private var magnifyBy = 1.0 Image("photo") .resizable().scaledToFit() .scaleEffect(magnifyBy) .gesture( MagnifyGesture() .updating($magnifyBy) { value, state, _ in state = value.magnification } ) ``` With persisted scale: ```swift @State private var currentScale = 1.0 @GestureState private var gestureScale = 1.0 Image("photo") .scaleEffect(currentScale * gestureScale) .gesture( MagnifyGesture(minimumScaleDelta: 0.01) .updating($gestureScale) { value, state, _ in state = value.magnification } .onEnded { value in currentScale = min(max(currentScale * value.magnification, 0.5), 5.0) } ) ``` ## RotateGesture (iOS 17+) `RotateGesture` is the newer alternative to `RotationGesture`. Tracks two-finger rotation angle. ```swift @State private var angle = Angle.zero Rectangle() .fill(.blue).frame(width: 200, height: 200) .rotationEffect(angle) .gesture( RotateGesture(minimumAngleDelta: .degrees(1)) .onChanged { value in angle = value.rotation } ) ``` With persisted rotation: ```swift @State private var currentAngle = Angle.zero @GestureState private var gestureAngle = Angle.zero Rectangle() .rotationEffect(currentAngle + gestureAngle) .gesture( RotateGesture() .updating($gestureAngle) { value, state, _ in state = value.rotation } .onEnded { value in currentAngle += value.rotation } ) ``` ## Gesture Composition ### `.simultaneously(with:)` — both gestures recognized at the same time ```swift let magnify = MagnifyGesture() .onChanged { value in scale = value.magnification } let rotate = RotateGesture() .onChanged { value in angle = value.rotation } Image("photo") .scaleEffect(scale) .rotationEffect(angle) .gesture(magnify.simultaneously(with: rotate)) ``` The value is `SimultaneousGesture.Value` with `.first` and `.second` optionals. ### `.sequenced(before:)` — first must succeed before second begins ```swift let longPressBeforeDrag = LongPressGesture(minimumDuration: 0.5) .sequenced(before: DragGesture()) .onEnded { value in guard case .second(true, let drag?) = value else { return } finalOffset.width += drag.translation.width finalOffset.height += drag.translation.height } ``` ### `.exclusively(before:)` — only one succeeds (first has priority) ```swift let doubleTapOrLongPress = TapGesture(count: 2) .map { ExclusiveResult.doubleTap } .exclusively(before: LongPressGesture() .map { _ in ExclusiveResult.longPress } ) .onEnded { result in switch result { case .first(let val): handleDoubleTap() case .second(let val): handleLongPress() } } ``` ## @GestureState `@GestureState` is a property wrapper that **automatically resets** to its initial value when the gesture ends. Use for transient feedback; use `@State` for values that persist. ```swift @GestureState private var dragOffset = CGSize.zero // resets to .zero @State private var position = CGSize.zero // persists Circle() .offset( x: position.width + dragOffset.width, y: position.height + dragOffset.height ) .gesture( DragGesture() .updating($dragOffset) { value, state, _ in state = value.translation } .onEnded { value in position.width += value.translation.width position.height += value.translation.height } ) ``` Custom reset with animation: `@GestureState(resetTransaction: Transaction(animation: .spring))` ## Adding Gestures to Views Three modifiers control gesture priority in the view hierarchy: | Modifier | Behavior | |---|---| | `.gesture()` | Default priority. Child gestures win over parent. | | `.highPriorityGesture()` | Parent gesture takes precedence over child. | | `.simultaneousGesture()` | Both parent and child gestures fire. | ```swift // Problem: parent tap swallows child tap VStack { Button("Child") { handleChild() } // never fires } .gesture(TapGesture().onEnded { handleParent() }) // Fix 1: Use simultaneousGesture on parent VStack { Button("Child") { handleChild() } } .simultaneousGesture(TapGesture().onEnded { handleParent() }) // Fix 2: Give parent explicit priority VStack { Text("Child") .gesture(TapGesture().onEnded { handleChild() }) } .highPriorityGesture(TapGesture().onEnded { handleParent() }) ``` ### GestureMask Control which gestures participate when using `.gesture(_:including:)`: ```swift .gesture(drag, including: .gesture) // only this gesture, not subviews .gesture(drag, including: .subviews) // only subview gestures .gesture(drag, including: .all) // default: this + subviews ``` ## Custom Gesture Protocol Create reusable gestures by conforming to `Gesture`: ```swift struct SwipeGesture: Gesture { enum Direction { case left, right, up, down } let minimumDistance: CGFloat let onSwipe: (Direction) -> Void init(minimumDistance: CGFloat = 50, onSwipe: @escaping (Direction) -> Void) { self.minimumDistance = minimumDistance self.onSwipe = onSwipe } var body: some Gesture { DragGesture(minimumDistance: minimumDistance) .onEnded { value in let h = value.translation.width, v = value.translation.height if abs(h) > abs(v) { onSwipe(h > 0 ? .right : .left) } else { onSwipe(v > 0 ? .down : .up) } } } } // Usage Rectangle().gesture(SwipeGesture { print("Swiped \($0)") }) ``` Wrap in a `View` extension for ergonomic API: ```swift extension View { func onSwipe(perform action: @escaping (SwipeGesture.Direction) -> Void) -> some View { gesture(SwipeGesture(onSwipe: action)) } } ``` ## Common Mistakes ### 1. Conflicting parent/child gestures ```swift // DON'T: Parent .gesture() conflicts with child tap VStack { Button("Action") { doSomething() } } .gesture(TapGesture().onEnded { parentAction() }) // DO: Use .simultaneousGesture() or .highPriorityGesture() VStack { Button("Action") { doSomething() } } .simultaneousGesture(TapGesture().onEnded { parentAction() }) ``` ### 2. Using @State instead of @GestureState for transient state ```swift // DON'T: @State doesn't auto-reset — view stays offset after gesture ends @State private var dragOffset = CGSize.zero DragGesture() .onChanged { value in dragOffset = value.translation } .onEnded { _ in dragOffset = .zero } // manual reset required // DO: @GestureState auto-resets when gesture ends @GestureState private var dragOffset = CGSize.zero DragGesture() .updating($dragOffset) { value, state, _ in state = value.translation } ``` ### 3. Not using .updating() for intermediate feedback ```swift // DON'T: No visual feedback during long press LongPressGesture(minimumDuration: 2.0) .onEnded { _ in showResult = true } // DO: Provide feedback while pressing @GestureState private var isPressing = false LongPressGesture(minimumDuration: 2.0) .updating($isPressing) { current, state, _ in state = current } .onEnded { _ in showResult = true } ``` ### 4. Using deprecated gesture types on iOS 17+ ```swift // DON'T: Deprecated since iOS 17 MagnificationGesture() // deprecated — use MagnifyGesture() // DO: Use newer gesture types MagnifyGesture() // iOS 17+ RotateGesture() // iOS 17+ (newer alternative to RotationGesture) ``` ### 5. Heavy computation in onChanged ```swift // DON'T: Expensive work called every frame (~60-120 Hz) DragGesture() .onChanged { value in let result = performExpensiveHitTest(at: value.location) let filtered = applyComplexFilter(result) updateModel(filtered) } // DO: Throttle or defer expensive work DragGesture() .onChanged { value in dragPosition = value.location // lightweight state update only } .onEnded { value in performExpensiveHitTest(at: value.location) // once at end } ``` ### 6. Using onTapGesture for actions that should be a Button ```swift // DON'T: onTapGesture has no accessibility traits, VoiceOver role, // Voice Control targeting, Switch Control scanning, or keyboard activation Text("Delete") .onTapGesture { deleteItem() } // DO: Button provides all of these automatically Button("Delete", role: .destructive) { deleteItem() } // DO: For custom visuals, use ButtonStyle instead of onTapGesture Button { toggleExpanded() } label: { CardView() } .buttonStyle(.plain) ``` Reserve `onTapGesture` for multi-tap (`count: 2+`), tap-location-dependent behavior, or adding tap recognition to non-interactive content that already has appropriate accessibility traits. ## Review Checklist - [ ] Correct gesture type: `MagnifyGesture`/`RotateGesture` (not deprecated `Magnification`/`Rotation` variants) - [ ] `@GestureState` used for transient values that should reset; `@State` for persisted values - [ ] `.updating()` provides intermediate visual feedback during continuous gestures - [ ] Parent/child conflicts resolved with `.highPriorityGesture()` or `.simultaneousGesture()` - [ ] `onChanged` closures are lightweight — no heavy computation every frame - [ ] Composed gestures use correct combinator: `simultaneously`, `sequenced`, or `exclusively` - [ ] Persisted scale/rotation clamped to reasonable bounds in `onEnded` - [ ] Custom `Gesture` conformances use `var body: some Gesture` (not `View`) - [ ] Gesture-driven animations use `.spring` or similar for natural deceleration - [ ] `GestureMask` considered when mixing gestures across view hierarchy levels - [ ] `onTapGesture` only used where `count > 1`, tap location, or coordinate space matters — plain single-tap actions use `Button` instead ## References - See [references/gesture-patterns.md](references/gesture-patterns.md) for drag-to-reorder, pinch-to-zoom, combined rotate+scale, velocity calculations, and SwiftUI/UIKit gesture interop. - [Gesture protocol](https://sosumi.ai/documentation/swiftui/gesture) - [TapGesture](https://sosumi.ai/documentation/swiftui/tapgesture) - [LongPressGesture](https://sosumi.ai/documentation/swiftui/longpressgesture) - [DragGesture](https://sosumi.ai/documentation/swiftui/draggesture) - [MagnifyGesture](https://sosumi.ai/documentation/swiftui/magnifygesture) - [RotateGesture](https://sosumi.ai/documentation/swiftui/rotategesture) - [GestureState](https://sosumi.ai/documentation/swiftui/gesturestate) - [Composing SwiftUI gestures](https://sosumi.ai/documentation/swiftui/composing-swiftui-gestures) - [Adding interactivity with gestures](https://sosumi.ai/documentation/swiftui/adding-interactivity-with-gestures)