CODEWITHSUNDEEP
iosswiftalamofire
Dan
Dan

Reputation: 4299

Making HTTP request with AlamoFire causes EXC_BAD_ACCESS

I'm working on a simple project to help learn Swift and I'm running into a problem that I think has deeper implications / learning opportunities (trying to look on the bright side).

The high-level problem is that when I POST JSON-encoded parameters using AlamoFire, a EXC_BAD_ACCESS error quickly appears in a separate line of code where I set one of the parameters (specifically CoreLocation Manager's "didUpdateLocations") ... here's the code:

In ViewController, I create a mutable dictionary:

var parameters = [String:AnyObject]()

And, for the didUpdateLocations event, I assign the updated latitude / longitude values to the respective keys in the mutable dictionary.

class ViewController: UIViewController, CLLocationManagerDelegate {
    let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate
    ...
    func locationManager(locManager: CLLocationManager!, didUpdateLocations locations: [AnyObject]!) {
        appDelegate.parameters["longitude"] = locManager.location.coordinate.longitude
        appDelegate.parameters["latitude"] = locManager.location.coordinate.latitude
    }

Finally, I have a periodic function (using NSTimer.scheduledTimerWithTimeInterval) that POSTs to a server.

func updatePost() {
    println("POSTing update")

    Alamofire.request(.POST, "http://server.co/endpoint",
            parameters: appDelegate.parameters, encoding: .JSON)
}

If I comment out the Alamofire POST, everything is fine. With the POST, I get the EXC_BAD_ACCESS error at the first line of the didUpdateLocations (where the longitude key is set)

I suspect it's something to do with how the parameters are converted by the encoding routine of Alamofire, but I have no idea why it would appear up in the didUpdateLocations function and not in the Alamofire call itself ...

Can anyone provide any insights? Thank you

Upvotes: 0

Views: 776

Answers (1)

Nate Cook
Nate Cook

Reputation: 93276

What's happening is that you have multiple threads trying to access a Dictionary at the same time. When you modify parameters in didUpdateLocations, it likely moves in memory while it's being read inside Alamofire, causing the EXC_BAD_ACCESS exception.

To solve this I would stop updating the parameters dictionary from within didUpdateLocations - add a latestLocation property to your view controller and update that instead. Then, inside updatePost, create your dictionary of parameters and pass it to Alamofire.request.

Upvotes: 2

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