objective-c - 没有互联网时位置管理器崩溃

Question

当用户连接到互联网时，程序运行正常。但是，当用户未连接时，应用程序崩溃并显示:

Error:The operation couldn’t be completed. (kCLErrorDomain error 8.)
fatal error: unexpectedly found nil while unwrapping an Optional value

我想在它崩溃之前捕获错误并显示一个警报 Controller

func locationManager(manager: CLLocationManager!, didUpdateLocations locations: [AnyObject]!) {
    CLGeocoder().reverseGeocodeLocation(manager.location, completionHandler: { (placemarks, error) -> Void in
        if (error != nil) {
            println("Error:" + error.localizedDescription)
        }
        if placemarks.count > 0 {
            let pm = placemarks[0] as CLPlacemark
            self.displayLocationInfo(pm)
            currentLoc = manager.location
            currentLocGeoPoint = PFGeoPoint(location:currentLoc)
            var query = PFQuery(className:"Restaurant") //default: Restaurant
            query.whereKey("RestaurantLoc", nearGeoPoint:currentLocGeoPoint, withinMiles:setDistanceMiles) //filter by miles
            query.limit = 1000 //limit number of results
            query.findObjectsInBackgroundWithBlock {
                (objects: [AnyObject]!, error: NSError!) -> Void in
                if objects.isEmpty {
                    //NO RESULTS
                    let alertController = UIAlertController(title: "Unavailable Area", message:
                        "This app is not available in your area yet. We'll try our best to have it up and running as soon as possible.", preferredStyle: UIAlertControllerStyle.Alert)
                    alertController.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default,handler: nil))
                    self.presentViewController(alertController, animated: true, completion: nil)
                    self.navigationController!.popViewControllerAnimated(true)
                } else {
                    newArray = objects
                }
                self.hideActivityIndicator(self.view)
            }
        } else {
            println("error: \(error)")
        }
    })
}

Answer 1

问题是您的if 语句。你是这样说的:

if (error != nil) {
    println("Error:" + error.localizedDescription)
}
if placemarks.count > 0 { // ...

嗯， 有一个错误。你被告诉有一个错误。但是你不听!你没有停下来!您就好像什么都没发生一样继续，并尝试访问 placemarks 变量——它没有被返回。您需要在此处使用逻辑，以便在出现错误时退出:

if (error != nil) {
    println("Error:" + error.localizedDescription)
    return // go no further!
}
if placemarks.count > 0 { // ...

但是请注意，最好先检查 placemarks 是否为 nil :

if placemarks == nil {
    // check error
    // return
}
if placemarks.count > 0 { // ...