Blog_TestingHealthKit.swift

import UIKit
import HealthKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
	
	var window: UIWindow?
	private let store = HKHealthStore()
	private let falls = HKObjectType.quantityType(forIdentifier: .numberOfTimesFallen)!
	private var lastAnchor: HKQueryAnchor?
	
	func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
		requestPermissionToDetectFalls()
		return true
	}
	
	private func requestPermissionToDetectFalls() {
		store.requestAuthorization(toShare: nil, read: [falls]) { success, error in
			print("Finished requesting authorization", success, error)
			self.observeFalls()
		}
	}
	
	private func observeFalls() {
		let query = HKObserverQuery(sampleType: falls, predicate: nil) { query, handler, error in
			self.checkNewFalls()
			handler()
		}
		store.execute(query)
	}
	
	private func checkNewFalls() {
		let query = HKAnchoredObjectQuery(type: falls, predicate: nil, anchor: lastAnchor, limit: HKObjectQueryNoLimit) { query, sample, deleted, anchor, error in
			defer { self.lastAnchor = anchor }
			guard self.lastAnchor != nil else { return }
			guard sample?.isEmpty == false else { return }
			self.presentFallAlert()
		}
		store.execute(query)
	}
	
	private func presentFallAlert() {
		DispatchQueue.main.async {
			let alert = UIAlertController(title: "You fell!", message: "Are you okay?", preferredStyle: .alert)
			alert.addAction(.init(title: "Yes, thanks!", style: .default))
			alert.addAction(.init(title: "No!", style: .default))
			self.window?.rootViewController?.present(alert, animated: true)
		}
	}
	
}