In SwiftUI how can I animate a Published View change? - swift

Question

I would like to animate a View change.
In particular, I have done a View where one of its children is a changing View.
struct MasterView: View {
#State var playerLeft: Bool = false
#ObservedObject var viewModel: MasterViewModel
var body: some View {
ZStack {
WaitPlayerBackView(isShowing: self.$playerLeft) {
self.viewModel.currentView
}
}
}
}
The view model is an ObservableObject class. currentView is changed by a method called from an async thread, like this:
class MasterViewModel: ObservableObject {
#Published var currentView: AnyView = AnyView(EmptyView())
func changeView() {
self.currentView = AnyView(NightView())
}
}
It's like a copy of Android fragments (pardon the comparison).
How can I animate this View change?
I have tried different options like:
self.viewModel.currentView.animate(.default)
or
struct MasterView: View {
#State var playerLeft: Bool = false
#ObservedObject var viewModel: MasterViewModel
var body: some View {
ZStack {
WaitPlayerBackView(isShowing: self.$playerLeft) {
self.viewModel.currentView
}
}.animate(self.viewModel.animate ? .easeIn(duration: 1) : .none)
}
}
class MasterViewModel: ObservableObject {
#Published var currentView: AnyView = AnyView(EmptyView())
#Published var animate = false
func changeView() {
self.animate = false
self.currentView = AnyView(NightView())
self.animate = true
}
}
However, none of them worked.
This is how I see a transition when changing the instance of currentView.

Answer 1

Moving your view initialization to MasterView makes everything easier:
struct MasterView: View {
#State var playerLeft: Bool = false
#ObservedObject var viewModel: MasterViewModel
var body: some View {
ZStack {
VStack { //this represents WaitPlayerBackView
if viewModel.day { //here are the posibles views that self.viewModel.currentView could have
Text("DayView").transition(AnyTransition.opacity.animation(.easeInOut(duration: 1.0)))
} else {
Text("NightView").transition(AnyTransition.opacity.animation(.(duration: 1.0)))
}
}
}
}
}
class MasterViewModel: ObservableObject {
#Published var day: Bool = false
init () {
_ = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(changeView), userInfo: nil, repeats: true) //Only for testing
}
#objc func changeView() { //#objc is only for testing
day.toggle()
}
}