Animatable

protocol · iOS 13.0+ · SDK 27.1

protocol Animatable

A type that describes how to animate a property of a view. When an animatable value changes inside a ``withAnimation(_:_:)`` block (or is affected by an ``animation(_:value:)`` modifier), SwiftUI reads the old and new ``animatableData`` values, then interpolates between them over successive frames using ``VectorArithmetic`` operations. The framework calls the ``animatableData`` setter on each frame, giving your type a chance to update any derived state. ### Use the Animatable macro To conform a type to the `Animatable` protocol, use the ``Animatable()`` macro to avoid writing the ``animatableData`` property by hand: @Animatable struct RingSegment: Shape { var startAngle: Angle var endAngle: Angle // ... } The macro inspects every stored property. Properties whose types conform to `VectorArithmetic` or `Animatable` are included in the synthesized ``animatableData``. If a property cannot participate, the macro emits an error suggesting you mark it with ``AnimatableIgnored()`` or conform its type to `VectorArithmetic` or `Animatable`: @Animatable struct RingSegment: Shape { var startAngle: Angle var endAngle: Angle @AnimatableIgnored var isOpaque: Bool // ... } ### Manual conformance for custom interpolation Reach for a handwritten ``animatableData`` when the interpolated value needs custom logic that does not correspond one-to-one with a stored property, such as normalization, clamping, or driving a derived value. Use ``AnimatableValues`` (26.0+ releases) to group multiple animated properties, or ``AnimatablePair`` on earlier deployment targets: struct WaveShape: Shape { var amplitude: CGFloat var phase: CGFloat var maxAmplitude: CGFloat var animatableData: AnimatableValues<CGFloat, CGFloat> { get { AnimatableValues(amplitude, phase) } set { amplitude = min( max(newValue.value.0, 0), maxAmplitude) phase = newValue.value.1 .truncatingRemainder( dividingBy: 2 * .pi) } } // ... }

Members (1)

var animatableData: EmptyAnimatableData { get set }

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