Alert close problem MRE.

AlertModifierWithoutProblem.swift

import SwiftUI

@main
struct ExampleApp: App {

    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

let colors: [Color] = [.red, .green, .blue, .orange, .yellow, .purple, .pink, .brown, .gray, .white]

struct ContentView: View {
    @State private var timer = Timer.publish(every: 0.05, on: .main, in: .common).autoconnect()
    @State private var isAlertPresented = false
    @State private var counter = 0

    var body: some View {
        let _ = Self._printChanges()
        VStack {
            Button("Show alert") {
                isAlertPresented = true
            }
            Rectangle()
                .frame(width: 10, height: 10)
                .foregroundStyle(colors[counter % colors.count])
        }
        .alert(
            "Alert",
            isPresented: $isAlertPresented,
            actions: {
                Button("OK") {}
            },
            message: {
                Text("Dismiss me.")
            }
        )
        .onReceive(timer) { _ in
            counter += 1
        }
    }
}

AlertProblemMRE.swift

import SwiftUI

@main
struct ExampleApp: App {

    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

let colors: [Color] = [.red, .green, .blue, .orange, .yellow, .purple, .pink, .brown, .gray, .white]

// Alert close problem MRE.
struct ContentView: View {
    @State private var timer = Timer.publish(every: 0.05, on: .main, in: .common).autoconnect()
    @State private var isAlertPresented = false
    @State private var counter = 0

    var body: some View {
        let _ = Self._printChanges()
        VStack {
            Button("Show alert") {
                isAlertPresented = true
            }
            Rectangle()
                .frame(width: 10, height: 10)
                .foregroundStyle(colors[counter % colors.count])
        }
        .alert(isPresented: $isAlertPresented) {
            Alert(
                title: Text("Alert"),
                message: Text("Dismiss me."),
                dismissButton: .default(Text("OK")) {
                    isAlertPresented = false
                }
            )
        }
        .onReceive(timer) { _ in
            counter += 1
        }
    }
}

AlertProblemObservableObjectMRE.swift

import SwiftUI

@main
struct ExampleApp: App {
    @State private var timer = Timer.publish(every: 0.05, on: .main, in: .common).autoconnect()
    @State private var counter = Counter()

    var body: some Scene {
        WindowGroup {
            ContentView()
                .environmentObject(counter)
                .onReceive(timer) { _ in
                    counter.value += 1
                }
        }
    }
}

let colors: [Color] = [.red, .green, .blue, .orange, .yellow, .purple, .pink, .brown, .gray, .white]

final class Counter: ObservableObject {
    @Published var value = 0
}

struct ContentView: View {
    // Even when it is not used in `body`, but only present in `View`, `body` is still constantly called.
    @EnvironmentObject var counter: Counter // Remove this line and compare result.
    @State private var isAlertPresented = false

    var body: some View {
        let _ = Self._printChanges()
        Button("Show alert") {
            isAlertPresented = true
        }
        .alert(isPresented: $isAlertPresented) {
            Alert(
                title: Text("Alert"),
                message: Text("Dismiss me."),
                dismissButton: .default(Text("OK")) {
                    isAlertPresented = false
                }
            )
        }
    }
}

OneOfPossibleSolutions.swift

import SwiftUI

@main
struct ExampleApp: App {

    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

let colors: [Color] = [.red, .green, .blue, .orange, .yellow, .purple, .pink, .brown, .gray, .white]

struct ContentView: View {
    @State private var timer = Timer.publish(every: 0.05, on: .main, in: .common).autoconnect()
    @State private var isAlertPresented = false
    @State private var counter = 0

    var body: some View {
        let _ = Self._printChanges()
        VStack {
            Button("Show alert") {
                isAlertPresented = true
            }
            // In this case the `IndicatorView` `body` is called constantly, not `ContentView`, like in AlertProblemMRE.swift
            IndicatorView(counter: $counter)
        }
        .alert(isPresented: $isAlertPresented) {
            Alert(
                title: Text("Alert"),
                message: Text("Dismiss me."),
                dismissButton: .default(Text("OK")) {}
            )
        }
        .onReceive(timer) { _ in
            counter += 1
        }
    }
}

struct IndicatorView: View {
    @Binding var counter: Int

    var body: some View {
        Rectangle()
            .frame(width: 10, height: 10)
            .foregroundStyle(colors[counter % colors.count])
    }
}