Build a basic Altimeter with SwiftUi for Apple Watch - xcode

Question

I am trying to build a MVP with SwiftUI that simply shows me the changes in altitude on my Apple Watch. From there I will figure out where to go next (I want to use it for paragliding and other aviation things).
I have previous experience in python, but nothing in Swift, so even after a ton of tutorials I am very unsure about how and where to declare and then use functionalities.
Here is my code so far:
//
// ContentView.swift
// Altimeter WatchKit Extension
//
// Created by Luke Crouch on 29.09.20.
//
import SwiftUI
import CoreMotion
//class func isRelativeAltitudeAvailable() -> Bool
struct ContentView: View {
let motionManager = CMMotionManager()
let queue = OperationQueue()
let altimeter = CMAltimeter()
let altitude = 0
var relativeAltitude: NSNumber = 0
var body: some View {
if motionManager.isRelativeAltitudeAvailable() {
switch CMAltimeter.authorizationStatus() {
case .notDetermined: // Handle state before user prompt
fatalError("Awaiting user prompt...")
case .restricted: // Handle system-wide restriction
fatalError("Authorization restricted!")
case .denied: // Handle user denied state
fatalError("Auhtorization denied!")
case .authorized: // Ready to go!
print("Authorized!")
#unknown default:
fatalError("Unknown Authorization Status")
}
altimeter.startRelativeAltitudeUpdates(to: queue, withHandler: CMAltitudeHandler)
}
// something like relative Altitude = queue[..]
Text("\(relativeAltitude)")
.font(.largeTitle)
.fontWeight(.bold)
.foregroundColor(Color.green)
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
I am getting multiple errors that I dont know how to deal with:
Type 'Void' cannot conform to 'View', only struct/enum/class types can conform to protocols.
Value of type CMMotionManager has no member 'isRelativeAltitudeAvailable'
Type '()' cannot conform to View...
Cannot convert value of type 'CMAltitudeHandler.Type' (aka '((Optional, Optional) -> ()).Type') to expected argument type 'CMAltitudeHandler' (aka '(Optional, Optional) -> ()')
Could you please give me some hints?
Thank you so much!
Luke

Answer 1

I figured it out after trying around a lot:
//
// ContentView.swift
// Altimeter WatchKit Extension
//
// Created by Lukas Wheldon on 29.09.20.
//
import SwiftUI
import CoreMotion
struct ContentView: View {
#State var relativeAltitude: NSNumber = 0
#State var altitude = 0
let altimeter = CMAltimeter()
func update(d: CMAltitudeData?, e: Error?){
print("altitude \(altitude)")
print("CMAltimeter \(altimeter)")
print("relative Altitude \(relativeAltitude))")
}
var body: some View {
VStack {
Text("\(altimeter)")
.fontWeight(.bold)
.foregroundColor(Color.green)
Button(action: {
print("START")
self.startAltimeter()
}, label: {
Text("Start Altimeter")
.bold()
.foregroundColor(.green)
})
}
}
func startAltimeter() {
if CMAltimeter.isRelativeAltitudeAvailable() {
switch CMAltimeter.authorizationStatus() {
case .notDetermined: // Handle state before user prompt
print("bb")
//fatalError("Awaiting user prompt...")
case .restricted: // Handle system-wide restriction
fatalError("Authorization restricted!")
case .denied: // Handle user denied state
fatalError("Authorization denied!")
case .authorized: // Ready to go!
let _ = print("Authorized!")
#unknown default:
fatalError("Unknown Authorization Status")
}
self.altimeter.startRelativeAltitudeUpdates(to: OperationQueue.main) {(data,error) in DispatchQueue.main.async {
print("\(altitude)")
print("\(relativeAltitude)")
}
}
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
Next steps will be to check if I can access the barometer raw data and calculate altitudes on that.