# AnimationContext Contextual values that a custom animation can use to manage state and access a view’s environment. ``` struct AnimationContext where Value : VectorArithmetic ``` ## Overview The system provides an `AnimationContext` to a [`CustomAnimation`](/documentation/SwiftUI/CustomAnimation) instance so that the animation can store and retrieve values in an instance of [`AnimationState`](/documentation/SwiftUI/AnimationState). To access these values, use the context’s [`state`](/documentation/SwiftUI/AnimationContext/state) property. For more convenient access to state, create an [`AnimationStateKey`](/documentation/SwiftUI/AnimationStateKey) and extend `AnimationContext` to include a computed property that gets and sets the [`AnimationState`](/documentation/SwiftUI/AnimationState) value. Then use this property instead of [`state`](/documentation/SwiftUI/AnimationContext/state) to retrieve the state of a custom animation. For example, the following code creates an animation state key named `PausableState`. Then the code extends `AnimationContext` to include the `pausableState` property: ``` private struct PausableState: AnimationStateKey { var paused = false var pauseTime: TimeInterval = 0.0 static var defaultValue: Self { .init() } } extension AnimationContext { fileprivate var pausableState: PausableState { get { state[PausableState.self] } set { state[PausableState.self] = newValue } } } ``` To access the pausable state, the custom animation `PausableAnimation` uses the `pausableState` property instead of the [`state`](/documentation/SwiftUI/AnimationContext/state) property: ``` struct PausableAnimation: CustomAnimation { let base: Animation func animate(value: V, time: TimeInterval, context: inout AnimationContext) -> V? where V : VectorArithmetic { let paused = context.environment.animationPaused let pausableState = context.pausableState var pauseTime = pausableState.pauseTime if pausableState.paused != paused { pauseTime = time - pauseTime context.pausableState = PausableState(paused: paused, pauseTime: pauseTime) } let effectiveTime = paused ? pauseTime : time - pauseTime let result = base.animate(value: value, time: effectiveTime, context: &context) return result } } ``` The animation can also retrieve environment values of the view that created the animation. To retrieve a view’s environment value, use the context’s [`environment`](/documentation/SwiftUI/AnimationContext/environment) property. For instance, the following code creates a custom [`EnvironmentValues`](/documentation/SwiftUI/EnvironmentValues) property named `animationPaused`, and the view `PausableAnimationView` uses the property to store the paused state: ``` extension EnvironmentValues { @Entry var animationPaused: Bool = false } struct PausableAnimationView: View { @State private var paused = false var body: some View { VStack { ... } .environment(\.animationPaused, paused) } } ``` Then the custom animation `PausableAnimation` retrieves the paused state from the view’s environment using the [`environment`](/documentation/SwiftUI/AnimationContext/environment) property: ``` struct PausableAnimation: CustomAnimation { func animate(value: V, time: TimeInterval, context: inout AnimationContext) -> V? where V : VectorArithmetic { let paused = context.environment.animationPaused ... } } ``` ## Topics ### Managing state [`var state: AnimationState`](/documentation/SwiftUI/AnimationContext/state) The current state of a custom animation. ### Retrieving view environment values [`var environment: EnvironmentValues`](/documentation/SwiftUI/AnimationContext/environment) The current environment of the view that created the custom animation. ### Creating context [`func withState(AnimationState) -> AnimationContext`](/documentation/SwiftUI/AnimationContext/withState(_:)) Creates a new context from another one with a state that you provide. ### Instance Properties [`var isLogicallyComplete: Bool`](/documentation/SwiftUI/AnimationContext/isLogicallyComplete) Set this to `true` to indicate that an animation is logically complete. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)