SwiftUI Animation on property change?

Question

I want to animate the appearance of an item in a list. The list looks like this:

Text("Jim") Text("Jonas") TextField("New Player") TextField("New Player") //should be animated when appearing (not shown until a name is typed in the first "New Player")

The last TextField should be hidden until newPersonName.count > 0 and then appear with an animation.

This is the code:

struct V_NewSession: View { @State var newPersonName: String = "" @State var participants: [String] = [ "Jim", "Jonas" ] var body: some View { VStack(alignment: .leading) { ForEach(0...self.participants.count + 1, id: \.self) { i in // Without this if statement, the animation works // but the Textfield shouldn't be shown until a name is typed if (!(self.newPersonName.count == 0 && i == self.participants.count + 1)) { HStack { if(i < self.participants.count) { Text(self.participants[i]) } else { TextField("New Player", text: $newPersonName, onEditingChanged: { focused in if (self.newPersonName.count == 0) { if (!focused) { handleNewPlayerEntry() } } }) } } } } .transition(.scale) Spacer() } } func handleNewPlayerEntry() { if(newPersonName.count > 0) { withAnimation(.spring()) { participants.append(newPersonName) newPersonName = "" } } } }

I know withAnimation(...) only applies to participants.append(newPersonName), but how can I get the animation to work on the property change in the if-statement? if ((!(self.newPersonName.count == 0 && i == self.participants.count + 1)).animation()) doesn't work.

I updated it and it compiles now

fer0n
– fer0n

2021-06-07 06:53:01 +00:00
Commented Jun 7, 2021 at 6:53 — fer0n
– fer0n, Commented Jun 7, 2021 at 6:53

jnpdx · Accepted Answer · 2021-06-06 20:04:28Z

Your example code won't compile for me, but here's a trivial example of using Combine inside a ViewModel to control whether a second TextField appears based on a condition:

 import SwiftUI import Combine class ViewModel : ObservableObject { @Published var textFieldValue1 = "" @Published var textFieldValue2 = "Second field" @Published var showTextField2 = false private var cancellable : AnyCancellable? init() { cancellable = $textFieldValue1.sink { value in withAnimation { self.showTextField2 = !value.isEmpty } } } } struct ContentView: View { @StateObject var viewModel = ViewModel() var body: some View { VStack { TextField("", text: $viewModel.textFieldValue1) .textFieldStyle(RoundedBorderTextFieldStyle()) if viewModel.showTextField2 { TextField("", text: $viewModel.textFieldValue2) .textFieldStyle(RoundedBorderTextFieldStyle()) .transition(.scale) } } } }

Hans Rietmann · Accepted Answer · 2021-06-06 20:22:49Z

Is that approaching what you're attempting to build ?

struct ContentView: View { @State var newPersonName: String = "" @State var participants: [String] = [ "Jim", "Jonas" ] @State var editingNewPlayer = false var body: some View { VStack(alignment: .leading, spacing: 16) { ForEach(participants, id: \.self) { participant in Text(participant) .padding(.trailing) Divider() } Button(action: handleNewPlayerEntry, label: { TextField("New Player", text: $newPersonName, onEditingChanged: { edit in editingNewPlayer = edit }, onCommit: handleNewPlayerEntry) }) if editingNewPlayer { Button(action: handleNewPlayerEntry, label: { TextField("New Player", text: $newPersonName) { edit in editingNewPlayer = false } }) } } .padding(.leading) .frame(maxHeight: .infinity, alignment: .top) .transition(.opacity) .animation(.easeIn) } func handleNewPlayerEntry() { if newPersonName.count > 0 { withAnimation(.spring()) { participants.append(newPersonName) newPersonName = "" editingNewPlayer = false } } } }

You might be on to the right answer, but since you didn't explain your code, we don't know. Perhaps you can explain your solution?

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