Message from debugger: Terminated due to memory issue

Question

My app working with Geojson file. I use MapBox SDK to add MGLPolyline to map. But the problem is my file too large, so that the app crash and got the error: Message from debugger: Terminated due to memory issue. I faced with 66234 objects at first loop. I tried to chunk the array to new array but not success. Please help me to solve the prolem. Here is my code for draw on map and here is my test project on github use Xcode 8.1 If have any different 3rd party which can solve my prolems is welcome too:

func drawPolyline() {

    // Parsing GeoJSON can be CPU intensive, do it on a background thread
    DispatchQueue.global(qos: .background).async {
        // Get the path for example.geojson in the app's bundle
        let jsonPath = Bundle.main.path(forResource: "KMLMAPNew", ofType: "json")
        let jsonData = NSData(contentsOfFile: jsonPath!)

        do {
            // Load and serialize the GeoJSON into a dictionary filled with properly-typed objects
            guard let jsonDict = try JSONSerialization.jsonObject(with: jsonData! as Data, options: []) as? Dictionary<String, AnyObject>, let features = jsonDict["features"] as? Array<AnyObject> else{return}

            for feature in features {
                guard let feature = feature as? Dictionary<String, AnyObject>, let geometry = feature["geometry"] as? Dictionary<String, AnyObject> else{ continue }

                if geometry["type"] as? String == "LineString" {
                    // Create an array to hold the formatted coordinates for our line
                    var coordinates: [CLLocationCoordinate2D] = []

                    if let locations = geometry["coordinates"] as? Array<AnyObject> {
                        // Iterate over line coordinates, stored in GeoJSON as many lng, lat arrays
                        for location in locations {
                            // Make a CLLocationCoordinate2D with the lat, lng
                            if let location = location as? Array<AnyObject>{
                                let coordinate = CLLocationCoordinate2DMake(location[1].doubleValue, location[0].doubleValue)

                                // Add coordinate to coordinates array
                                coordinates.append(coordinate)
                            }
                        }
                    }

                    let line = MGLPolyline(coordinates: &coordinates, count: UInt(coordinates.count))

                    // Optionally set the title of the polyline, which can be used for:
                    //  - Callout view
                    //  - Object identification
                    line.title = "Crema to Council Crest"

                    // Add the annotation on the main thread
                    DispatchQueue.main.async {
                        // Unowned reference to self to prevent retain cycle
                        [unowned self] in
                        self.mapboxView.addAnnotation(line)
                    }
                }
            }
        }
        catch
        {
            print("GeoJSON parsing failed")
        }
    }
}

EDIT::@Alessandro Ornano and @fragilecat thanks so much. But those solutions still cannot solve the terminate of the app on iPad. I think it so hard to change the current code to get it to work properly, because the data is so large. I think I will need another solution that works with big data. Like chunking the array into the small arrays then loading them by queue. But I don't know how to start :(

I send an email to the support team at MapBox, asking for suggestions.

Answer 1

One thing I have learnt from creating memory intensive apps is that you have to use autoreleasepool every time you create variables inside loops, if these loops are long

Review all your code and transform things like

func loopALot() {
    for _ in 0 ..< 5000 {
        let image = NSImage(contentsOfFile: filename)
    }
}

into

func loopALot() {
    for _ in 0 ..< 5000 {
      autoreleasepool {
        let image = NSImage(contentsOfFile: filename)
      }
    }
}

Review all kinds of loops for, while, etc.

This will force of iOS to release the variable and its correspondent memory usage at the end of every turn of the loop, instead of holding the variable and its memory usage until the function ends. That will reduce dramatically your memory usage.