SwiftUI Button if Statement - if-statement

Question

I have the following problem:
I built an app that has 6 buttons and each of these buttons is assigned a CL region.
I have a GPS track file that provides the app with locations and simulates a walk.
Now buttons should turn yellow when the region assigned to them is reached. It works so far, but the problem is that I don't know where to ask whether or not to reach the Region of Button.
I tried .onAppear () {if ...}, but that is only triggered once and I need something that monitors the If statement all the time.
Is there anything?
Thanks in advance
here my code:
import MapKit
import SwiftUI
import CoreLocation
var region1 = CLCircularRegion(center:CLLocationCoordinate2D(latitude: 52.505088, longitude: 13.333574), radius: 20, identifier: "region1")
var region2 = CLCircularRegion(center:CLLocationCoordinate2D(latitude: 52.504829, longitude: 13.336798), radius: 20, identifier: "region2")
var region3 = CLCircularRegion(center:CLLocationCoordinate2D(latitude: 52.504733, longitude: 13.341834), radius: 20, identifier: "region3")
var region4 = CLCircularRegion(center:CLLocationCoordinate2D(latitude: 52.503312, longitude: 13.347718), radius: 20, identifier: "region4")
var region5 = CLCircularRegion(center:CLLocationCoordinate2D(latitude: 52.505699, longitude: 13.352198), radius: 20, identifier: "region5")
var region6 = CLCircularRegion(center:CLLocationCoordinate2D(latitude: 52.513517, longitude: 13.350253), radius: 20, identifier: "region6")
class LocationEnviroment: NSObject, CLLocationManagerDelegate, ObservableObject{
var locationManager = CLLocationManager()
#Published var currentPosition = ""
var Waypoints = [region1, region2, region3, region4, region5, region6];
#Published var RegionIndex: Int = 6
func initPositionService(){
locationManager.desiredAccuracy = kCLLocationAccuracyBest
locationManager.requestAlwaysAuthorization()
locationManager.requestWhenInUseAuthorization()
locationManager.delegate = self
locationManager.startUpdatingLocation()
}
func isWayPoint(mylocation : CLLocation) -> Int{
for i in self.Waypoints{
if(i == mylocation){
if(i.identifier == "region1"){
return 0
}else if(i.identifier == "region2"){
return 1
}else if(i.identifier == "region3"){
return 2
}else if(i.identifier == "region4"){
return 3
}else if(i.identifier == "region5"){
return 4
}else if(i.identifier == "region6"){
return 5
}
}
}
return 6 // <- nothing found
}
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
let myLocation = locations.last
let lat = myLocation?.coordinate.latitude
let lon = myLocation?.coordinate.longitude
self.currentPosition = "lat: \(lat ?? 0) lon: \(lon ?? 0)"
self.RegionIndex = isWayPoint(mylocation: myLocation!)
}
}
struct ContentView: View {
#StateObject var locationEnviroment = LocationEnviroment()
var Todo = ["Friseur / Haare schneiden", "Dönerbude / zu Mittag essen", "Bank / Geld abheben", "Supermarkt / einkaufen", "Blumeneladen /\n Blumen kaufen", " Lisa's Wohnung /\n Lisa Blumen überreichen" ]
#State private var disabled = Array(repeating: true, count: 6)
#State private var red = 255.0
#State private var blue = 0.0
#State private var green = 0.0
var body: some View {
VStack(alignment: .center, spacing: 10){
Text(locationEnviroment.currentPosition)
.padding()
ForEach(0..<6) { row in
Button(action : {
if(disabled[row] == false){
red = 0.0
green = 255.0
blue = 0.0
}
}) {
Text(Todo[row])
.frame(width : 200, height: 40, alignment: .center)
.clipShape(Rectangle())
.padding()
.border(Color.black, width: 1)
.font(.system(size: 15))
.foregroundColor(.black)
}
.background(Color(red: red/255, green: green/255, blue: blue/255))
.lineLimit(nil)
.cornerRadius(8.0)
.disabled(disabled[row])
.onAppear(){
if(locationEnviroment.RegionIndex == row){
disabled[row] = false
red = 255.0
green = 255.0
blue = 0.0
}
}
}
}
.onAppear(){
locationEnviroment.initPositionService()
}
}
}

Answer 1

You can use onChange to monitor the status of RegionIndex. It might look like this (replacing your onAppear):
.onChange(of: locationEnviroment.RegionIndex) { regionIndex in
if regionIndex == row {
disabled[row] = false
red = 255.0
green = 255.0
blue = 0.0
}
}
A couple of side notes:
Generally in Swift, variable and property names start with lowercase letters
You may want to investigate using computed properties to change/determine the colors. I started writing a solution with those but then realized I didn't totally understand what the full logic of the color system was, especially with the interaction between pressing and disabling the buttons. But, in general, your view will re-render any time a #Published property on your #StateObject changes, so you don't necessarily have to use something like onChange to trigger an update.