Animating date changes in SwiftUI

Question

I am struggling to create an animation of a changing date value. A simplified example is below. It is intended to update the Text view with changing values as the date is updated from its original value to its new value. Help would be most appreciated!

struct DateAnimationView: View { @State var date = Date() typealias AnimatableData = Date var animatableData: Date{ get{date} set{date = newValue} } var body: some View { VStack{ Text(date, style: .time) .padding() Button(action:{ withAnimation(.linear(duration: 3.0)){ date.addTimeInterval(60 * 60 * 3) } }){ Text("Add 3 hours") } .padding() Spacer() } } }

Another attempt which also fails:

struct InnerView: View { var date: Date var interval: TimeInterval typealias AnimatableData = TimeInterval var animatableData: TimeInterval{ get{interval} set{interval = newValue} } var body: some View{ Text(date.addingTimeInterval(interval), style: .time) } } struct DateAnimationView: View{ @State var isOn: Bool = false var body: some View{ VStack{ InnerView(date: Date(), interval: isOn ? 60*60*3 : 0) Button(action:{ isOn.toggle() }){ Text("Go") } } } }

rohanphadte · Accepted Answer · 2020-10-29 19:48:43Z

The essential idea is that you need to specify an id for the component you're animating. SwiftUI uses this id to understand if it's the same component or a new component when doing a redraw. If it is a new component, it will remove the old one and add a new with the animation. The code below achieves the animation.

struct DateAnimationView: View { @State var date = Date() typealias AnimatableData = Date var animatableData: Date{ get{date} set{date = newValue} } var body: some View { VStack{ Text(date, style: .time) .padding() .id(String(date.hashValue)) Button(action:{ withAnimation(.linear(duration: 3.0)){ date.addTimeInterval(60 * 60 * 3) } }){ Text("Add 3 hours") } .padding() Spacer() } } }

A similar issue is solved by the solution posted here.

thanks for the quick response. Unfortunately, adding the id does not seem to work as expected. Now the two date values are simply superimposed. To be clear, I am hoping to see the text "count up" time values as it approaches the new time. (ie: 8:13 -> 8:42 -> 9:15 -> 10:22 -> 11:13)

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