Count distance on polyline swift

Question

I've created a map where you can press a start button. The application will then zoom in to your current location, and update the coordinate every 10 second and insert into an array of coordinates. Once I press the stop button, I've a polyline which draws lines between all coordinates. (Like the image below)

So my question is now: How can I count the distance the polyline was drawn?

//Draw polyline on the map
let aPolyLine = MKPolyline(coordinates: self.locations, count: self.locations.count)

    //Adding polyline to mapview
    self.mapView.addOverlay(aPolyLine)

    let startResult = self.locations.startIndex
    let stopResult = self.locations.endIndex

    //Retrieve distance and convert into kilometers
    let distance = startResult.distance(to: stopResult)
    let result = Double(distance) / 1000
    let y = Double(round(10 * result)) / 10
    self.KiloMeters.text = String(y) + " km"

My guess is that I cannot use startResult.distnace(to: stopResult) because, if I walk in a circle, the kilometer will show 0? right? I'm not sure, but it still dosent work. Nothing is showing when using the code like I've.

You have an array of locations. Iterate through the array, finding the distance between each point and the next. Total those distances — Paulw11, Mar 12 '19 at 11:14
@Paulw11 Do you mind adding a code example? I've no idea where to start lol — Putte, Mar 12 '19 at 11:25
@JoakimDanielson I'm using the distance(to:) atm. Why would it change if I use (from:) — Putte, Mar 12 '19 at 11:32
Not sure what distance(to:) is but if it works for you then use that instead otherwise as I said the other function is in the CLLocation class. — Joakim Danielson, Mar 12 '19 at 11:36
@Putte, this `distance(to:)` you're using is actually method of `Array.Index` type, which is `Int` right now. [And this function just returns difference between two indexes](https://developer.apple.com/documentation/swift/int/1641606-distance). For `.startIndex` and `.endIndex` of `Array` it would be just length of array. — user28434'mstep, Mar 12 '19 at 11:56

score 3 · Accepted Answer · answered Mar 12 '19 at 11:51

3

class ViewController: UIViewController, CLLocationManagerDelegate, MKMapViewDelegate {
    // MARK: - Variables
    let locationManager = CLLocationManager()

    // MARK: - IBOutlet
    @IBOutlet weak var mapView: MKMapView!

    // MARK: - IBAction
    @IBAction func distanceTapped(_ sender: UIBarButtonItem) {
        let locations: [CLLocationCoordinate2D] = [...]
        var total: Double = 0.0
        for i in 0..<locations.count - 1 {
            let start = locations[i]
            let end = locations[i + 1]
            let distance = getDistance(from: start, to: end)
            total += distance
        }
        print(total)
    }

    func getDistance(from: CLLocationCoordinate2D, to: CLLocationCoordinate2D) -> CLLocationDistance {
        // By Aviel Gross
        // https://stackoverflow.com/questions/11077425/finding-distance-between-cllocationcoordinate2d-points
        let from = CLLocation(latitude: from.latitude, longitude: from.longitude)
        let to = CLLocation(latitude: to.latitude, longitude: to.longitude)
        return from.distance(from: to)
    }
}

answered Mar 12 '19 at 11:51

El Tomato

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Instead of "distanceTapped" I can add that code in my play button? to make it automatic? Thanks a lot for your input, Ill look into this – Putte Mar 12 '19 at 11:53
1

Yes. You have to come with locations, an array of CLLocationCoordinate2D, for yourself, as per your code, though. – El Tomato Mar 12 '19 at 12:09
Seems like its working fine! The result is now: 4.5668457328325329. (It's 4 meter). How can I remove the ".5668457328325329"? Do you know? I've tried to /1000 etc, but not really working correctly – Putte Mar 12 '19 at 12:20
Use modf. https://stackoverflow.com/questions/31396301/getting-the-decimal-part-of-a-double-in-swift – El Tomato Mar 12 '19 at 12:22
@Putte, are you sure you want to round it down? Because it's closer to `5` than to `4`. – user28434'mstep Mar 12 '19 at 12:28
@user28434 Oh well, that's true. I just wanna hide the decimals, that's all. :) – Putte Mar 12 '19 at 12:29

Count distance on polyline swift

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