Button handling in SwiftUI

Here is a solution for the first part of your question: Three buttons where the last one tapped gets highlighted with a background:

import SwiftUI

struct ContentView: View {

    enum HighlightTag {
        case none, first, second, third
    }

    @State private var highlighted = HighlightTag.none

    var body: some View {
        VStack {
            Button("First") {
                highlighted = .first
            }.background(
                Color.accentColor.opacity(
                    highlighted == .first ? 0.2 : 0.0
                )
            )
            Button("Second") {
                highlighted = .second
            }.background(
                Color.accentColor.opacity(
                    highlighted == .second ? 0.2 : 0.0
                )
            )
            Button("Third") {
                highlighted = .third
            }.background(
                Color.accentColor.opacity(
                    highlighted == .third ? 0.2 : 0.0
                )
            )
        }
    }
}

Update: After reviewing your sample code on GitHub, I tried to understand your code, I tried to make some simplifications and tried to find a working solution.

Here are some opinions:

• The Attribute "@State" in front of "var butnsPool" is not needed and confusing.
• The Attribute "@State" in front of "var initialHilight" is not needed and confusing.
• Your ActiveButton stores a copy of the selected Button View because it is a struct which is probably the main reason for the strange behaviour.
• The needInit in your ObservableObject smells bad at least. If you really need to initialize something, you may consider doing it with some .onAppear() modifier in you ContentView.
• There is probably no need to use .environmentObject and @EnvironmentObject. You could consider using a parameter and @ObsservedObject
• There is probably no need for the ActiveButton at all, if you only use it internally. You could consider using a @State with the selected utton name
• Your BtnTxtView is fine, but consider replacing the conditional (func if) with some animatable properties, if you want to animate the transition.

Based on your code I created a much simpler and working solution.

I removed the ActiveButton class and also the BttnView struct. And I replaced the ContentView with this:

struct ContentView: View {
    var butnsPool: [String]
    var initialHilight: Int
    @State var selectedBox: String = ""

    var body: some View {
        ForEach(butnsPool, id: \.self) { buttonName in
            Button(action: {
                selectedBox = buttonName
            })
            {
                BtnTxtView(theLabel: buttonName,
                           highLight: buttonName == selectedBox)
            }
        }.onAppear {
            selectedBox = butnsPool[initialHilight]
        }
    }
}