SwiftUI Animation (iOS 26+)

Review, write, and fix SwiftUI animations. Apply modern animation APIs with correct timing, transitions, and accessibility handling using Swift 6.3 patterns.

Contents

• Triage Workflow
• withAnimation (Explicit Animation)
• Implicit Animation
• Spring Type (iOS 17+)
• PhaseAnimator (iOS 17+)
• KeyframeAnimator (iOS 17+)
• @Animatable Macro
• matchedGeometryEffect (iOS 14+)
• Navigation Zoom Transition (iOS 18+)
• Transitions (iOS 17+)
• ContentTransition (iOS 16+)
• Symbol Effects (iOS 17+)
• Symbol Rendering Modes
• Common Mistakes
• Review Checklist
• References

Triage Workflow

Step 1: Identify the animation category

withAnimation

.animation(_:body:)

.animation(_:value:)

PhaseAnimator

KeyframeAnimator

matchedGeometryEffect

matchedTransitionSource

.navigationTransition(.zoom)

.transition()

.contentTransition()

.symbolEffect()

CustomAnimation

Step 2: Choose the animation curve

// Timing curves
.linear                              // constant speed
.easeIn(duration: 0.3)              // slow start
.easeOut(duration: 0.3)             // slow end
.easeInOut(duration: 0.3)           // slow start and end

// Spring presets (preferred for natural motion)
.smooth                              // no bounce, fluid
.smooth(duration: 0.5, extraBounce: 0.0)
.snappy                              // small bounce, responsive
.snappy(duration: 0.4, extraBounce: 0.1)
.bouncy                              // visible bounce, playful
.bouncy(duration: 0.5, extraBounce: 0.2)

// Custom spring
.spring(duration: 0.5, bounce: 0.3, blendDuration: 0.0)
.spring(Spring(duration: 0.6, bounce: 0.2), blendDuration: 0.0)
.interactiveSpring(response: 0.15, dampingFraction: 0.86)

Step 3: Apply and verify

• Confirm animation triggers on the correct state change.
• Test with Accessibility > Reduce Motion enabled.
• Verify no expensive work runs inside animation content closures.

withAnimation (Explicit Animation)

withAnimation(.spring) { isExpanded.toggle() }

// With completion (iOS 17+)
withAnimation(.smooth(duration: 0.35), completionCriteria: .logicallyComplete) {
    isExpanded = true
} completion: { loadContent() }

Implicit Animation

Prefer

.animation(_:body:)

.animation(_:value:)

Badge()
    .foregroundStyle(isActive ? .green : .secondary)
    .animation(.snappy) { content in
        content
            .scaleEffect(isActive ? 1.15 : 1.0)
            .opacity(isActive ? 1.0 : 0.7)
    }

Circle()
    .scaleEffect(isActive ? 1.2 : 1.0)
    .opacity(isActive ? 1.0 : 0.6)
    .animation(.bouncy, value: isActive)

Spring Type (iOS 17+)

Four initializer forms for different mental models.

// Perceptual (preferred)
Spring(duration: 0.5, bounce: 0.3)

// Physical
Spring(mass: 1.0, stiffness: 100.0, damping: 10.0)

// Response-based
Spring(response: 0.5, dampingRatio: 0.7)

// Settling-based
Spring(settlingDuration: 1.0, dampingRatio: 0.8)

Three presets mirror Animation presets:

.smooth

.snappy

.bouncy

PhaseAnimator (iOS 17+)

Cycle through discrete phases with per-phase animation curves.

enum PulsePhase: CaseIterable {
    case idle, grow, shrink
}

struct PulsingDot: View {
    var body: some View {
        PhaseAnimator(PulsePhase.allCases) { phase in
            Circle()
                .frame(width: 40, height: 40)
                .scaleEffect(phase == .grow ? 1.4 : 1.0)
                .opacity(phase == .shrink ? 0.5 : 1.0)
        } animation: { phase in
            switch phase {
            case .idle: .easeIn(duration: 0.2)
            case .grow: .spring(duration: 0.4, bounce: 0.3)
            case .shrink: .easeOut(duration: 0.3)
            }
        }
    }
}

Trigger-based variant runs one cycle per trigger change:

PhaseAnimator(PulsePhase.allCases, trigger: tapCount) { phase in
    // ...
} animation: { _ in .spring(duration: 0.4) }

KeyframeAnimator (iOS 17+)

Animate multiple properties along independent timelines.

struct AnimValues {
    var scale: Double = 1.0
    var yOffset: Double = 0.0
    var opacity: Double = 1.0
}

struct BounceView: View {
    @State private var trigger = false

    var body: some View {
        Image(systemName: "star.fill")
            .font(.largeTitle)
            .keyframeAnimator(
                initialValue: AnimValues(),
                trigger: trigger
            ) { content, value in
                content
                    .scaleEffect(value.scale)
                    .offset(y: value.yOffset)
                    .opacity(value.opacity)
            } keyframes: { _ in
                KeyframeTrack(\.scale) {
                    SpringKeyframe(1.5, duration: 0.3)
                    CubicKeyframe(1.0, duration: 0.4)
                }
                KeyframeTrack(\.yOffset) {
                    CubicKeyframe(-30, duration: 0.2)
                    CubicKeyframe(0, duration: 0.4)
                }
                KeyframeTrack(\.opacity) {
                    LinearKeyframe(0.6, duration: 0.15)
                    LinearKeyframe(1.0, duration: 0.25)
                }
            }
            .onTapGesture { trigger.toggle() }
    }
}

Keyframe types:

LinearKeyframe

CubicKeyframe

SpringKeyframe

MoveKeyframe

Use

repeating: true

@Animatable Macro

Replaces manual

AnimatableData

// Replaces manual AnimatableData boilerplate
@Animatable
struct WaveShape: Shape {
    var frequency: Double
    var amplitude: Double
    var phase: Double
    @AnimatableIgnored var lineWidth: CGFloat

    func path(in rect: CGRect) -> Path {
        // draw wave using frequency, amplitude, phase
    }
}

Rules:

• Stored properties must conform to

  VectorArithmetic

  .
• Use

  @AnimatableIgnored

  to exclude non-animatable properties.
• Computed properties are never included.

matchedGeometryEffect (iOS 14+)

Synchronize geometry between views for shared-element animations.

struct HeroView: View {
    @Namespace private var heroSpace
    @State private var isExpanded = false

    var body: some View {
        if isExpanded {
            DetailCard()
                .matchedGeometryEffect(id: "card", in: heroSpace)
                .onTapGesture {
                    withAnimation(.spring(duration: 0.4, bounce: 0.2)) {
                        isExpanded = false
                    }
                }
        } else {
            ThumbnailCard()
                .matchedGeometryEffect(id: "card", in: heroSpace)
                .onTapGesture {
                    withAnimation(.spring(duration: 0.4, bounce: 0.2)) {
                        isExpanded = true
                    }
                }
        }
    }
}

Exactly one view per ID must be visible at a time for the interpolation to work.

Navigation Zoom Transition (iOS 18+)

Pair

matchedTransitionSource

.navigationTransition(.zoom(...))

struct GalleryView: View {
    @Namespace private var zoomSpace
    let items: [GalleryItem]

    var body: some View {
        NavigationStack {
            ScrollView {
                LazyVGrid(columns: [GridItem(.adaptive(minimum: 100))]) {
                    ForEach(items) { item in
                        NavigationLink {
                            GalleryDetail(item: item)
                                .navigationTransition(
                                    .zoom(sourceID: item.id, in: zoomSpace)
                                )
                        } label: {
                            ItemThumbnail(item: item)
                                .matchedTransitionSource(
                                    id: item.id, in: zoomSpace
                                )
                        }
                    }
                }
            }
        }
    }
}

Apply

.navigationTransition

Transitions (iOS 17+)

Control how views animate on insertion and removal.

if showBanner {
    BannerView()
        .transition(.move(edge: .top).combined(with: .opacity))
}

Built-in types:

.opacity

.slide

.scale

.scale(_:anchor:)

.move(edge:)

.push(from:)

.offset(x:y:)

.identity

.blurReplace

.blurReplace(_:)

.symbolEffect

.symbolEffect(_:options:)

Asymmetric transitions:

.transition(.asymmetric(
    insertion: .push(from: .bottom),
    removal: .opacity
))

ContentTransition (iOS 16+)

Animate in-place content changes without insertion/removal.

Text("\(score)")
    .contentTransition(.numericText(countsDown: false))
    .animation(.snappy, value: score)

// For SF Symbols
Image(systemName: isMuted ? "speaker.slash" : "speaker.wave.3")
    .contentTransition(.symbolEffect(.replace.downUp))

Types:

.identity

.interpolate

.opacity

.numericText(countsDown:)

.numericText(value:)

.symbolEffect

Symbol Effects (iOS 17+)

Animate SF Symbols with semantic effects.

// Discrete (triggers on value change)
Image(systemName: "bell.fill")
    .symbolEffect(.bounce, value: notificationCount)

Image(systemName: "arrow.clockwise")
    .symbolEffect(.wiggle.clockwise, value: refreshCount)

// Indefinite (active while condition holds)
Image(systemName: "wifi")
    .symbolEffect(.pulse, isActive: isSearching)

Image(systemName: "mic.fill")
    .symbolEffect(.breathe, isActive: isRecording)

// Variable color with chaining
Image(systemName: "speaker.wave.3.fill")
    .symbolEffect(
        .variableColor.iterative.reversing.dimInactiveLayers,
        options: .repeating,
        isActive: isPlaying
    )

All effects:

.bounce

.pulse

.variableColor

.scale

.appear

.disappear

.replace

.breathe

.rotate

.wiggle

Scope:

.byLayer

.wholeSymbol

Symbol Rendering Modes

Control how SF Symbol layers are colored with

.symbolRenderingMode(_:)

.monochrome

.hierarchical

.multicolor

.palette

.foregroundStyle

// Hierarchical — single tint, opacity layers for depth
Image(systemName: "speaker.wave.3.fill")
    .symbolRenderingMode(.hierarchical)
    .foregroundStyle(.blue)

// Palette — custom color per layer
Image(systemName: "person.crop.circle.badge.plus")
    .symbolRenderingMode(.palette)
    .foregroundStyle(.blue, .green)

// Multicolor — system-defined colors
Image(systemName: "cloud.sun.rain.fill")
    .symbolRenderingMode(.multicolor)

Variable color:

.symbolVariableColor(value:)

Image(systemName: "wifi")
    .symbolVariableColor(value: signalStrength) // 0.0–1.0

Docs: SymbolRenderingMode · symbolRenderingMode(_:)

Common Mistakes

1. Using bare

.animation(_:)

when you need precise scope

// TOO BROAD — applies when the view changes
.animation(.easeIn)

// CORRECT — bind animation to one value
.animation(.easeIn, value: isVisible)

// CORRECT — scope animation to selected modifiers
.animation(.easeIn) { content in
    content.opacity(isVisible ? 1.0 : 0.0)
}

2. Expensive work inside animation closures

Never run heavy computation in

keyframeAnimator

PhaseAnimator

3. Missing reduce motion support

@Environment(\.accessibilityReduceMotion) private var reduceMotion
withAnimation(reduceMotion ? .none : .bouncy) { showDetail = true }

4. Multiple matchedGeometryEffect sources

Only one view per ID should be visible at a time. Two visible views with the same ID causes undefined layout.

5. Using DispatchQueue or UIView.animate

// WRONG
DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) { withAnimation { isVisible = true } }
// CORRECT
withAnimation(.spring.delay(0.5)) { isVisible = true }

6. Forgetting animation on ContentTransition

// WRONG — no animation, content transition has no effect
Text("\(count)").contentTransition(.numericText(countsDown: true))
// CORRECT — pair with animation
Text("\(count)")
    .contentTransition(.numericText(countsDown: true))
    .animation(.snappy, value: count)

7. navigationTransition on wrong view

Apply

.navigationTransition(.zoom(sourceID:in:))

Review Checklist

• Animation curve matches intent (spring for natural, ease for mechanical)

• withAnimation

  wraps the state change; implicit animation uses

  .animation(_:body:)

  for selective modifier scope or

  .animation(_:value:)

  with an explicit value

• matchedGeometryEffect

  has exactly one source per ID; zoom uses matching

  id

  /

  namespace

• @Animatable

  macro used instead of manual

  animatableData

• accessibilityReduceMotion

  checked; no

  DispatchQueue

  /

  UIView.animate

• Transitions use

  .transition()

  ;

  contentTransition

  is paired with animation and uses the narrowest implicit animation scope that fits
• Animated state changes on @MainActor; animation-driving types are Sendable

References

• See references/animation-advanced.md for CustomAnimation protocol, full Spring variants, all Transition types, symbol effect details, Transaction system, UnitCurve types, and performance guidance.
• Core Animation bridging patterns: references/core-animation-bridge.md