example for using the Position library bearing utility functions

DirectionView

//
//  DirectionView.swift
//
//  The MIT License (MIT)
//
//  Copyright (c) 2020-present patrick piemonte (http://patrickpiemonte.com/)
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the Software is
//  furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in all
//  copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
//  SOFTWARE.
//
import UIKit
import Foundation
import CoreLocation.CLLocation
import Position

public final class DirectionView: UIView {

    // MARK: - ivars
    private lazy var _indicator: UIImageView = {
        let view = UIImageView(image: UIImage(named: "direction_indicator")?.withRenderingMode(UIImage.RenderingMode.alwaysTemplate))
        view.translatesAutoresizingMaskIntoConstraints = false
        view.tintColor = .black
        return view
    }()
    private var _location: CLLocation?
    private var _accuracyAnimator: UIViewPropertyAnimator?

    // MARK: - object lifecycle
    override public init(frame: CGRect) {
        super.init(frame: frame)
        setup()
    }

    public required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        setup()
    }

    deinit {
        LocationManager.shared.removeHeadingObserver(self)
    }

}

extension DirectionView {

    private func setup() {
        addSubview(_indicator)

        _accuracyAnimator = UIViewPropertyAnimator(duration: 0.15, curve: .easeInOut) {
            self._indicator.alpha = 0.25
        }

        _indicator.alpha = 0
    }

    public func config(_ targetLocation: CLLocation) {
        _location = targetLocation
        LocationManager.shared.addHeadingObserver(self)
        UIView.animate(withDuration: 0.15, delay: 0, options: .curveEaseIn) {
            self._indicator.alpha = 1
        } completion: { _ in
        }
    }

}

// MARK: - LocationManagerHeadingObserver
extension DirectionView: LocationManagerHeadingObserver {

    public func locationManager(_ locationManager: LocationManager, didUpdateHeading heading: CLHeading) {
        guard let targetLocation = _location else { return }
        guard let currentLocation = LocationContext.shared.lastLocation else { return // fade }
        if heading.headingAccuracy >= 0,
           let angle = currentLocation.bearingInRadians(toLocation: targetLocation, heading: heading) {
            UIView.animate(withDuration: 0.25) { [weak self] in
                guard let self = self else { return }
                self._indicator.transform = CGAffineTransform(rotationAngle: angle)
            } 
        } else {
            // fade indicator (not accurate)
        }
    }

}