Why do I get fatal error: unexpectedly found nil while unwrapping an Optional value when trying to go to mapView? [duplicate] - ios

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What does "Fatal error: Unexpectedly found nil while unwrapping an Optional value" mean?
(16 answers)
Closed 6 years ago.
I'm working on an app Witch has a list of places (added by the user) and a map view with a button to add the users curent location. the app works to this point. When the user taps on a place in the tableView the app should go to the mapView and show the place on the map with a pin . but when I do that the app crashes and gives me the following error unless the user has renamed the place and if they have, it works perfectly :
fatal error: unexpectedly found nil while unwrapping an Optional value
(lldb)
note that the crash occurs in the mapView on the line that says:
let latitude = NSString(string: places[activePlace]["lat"]!).doubleValue
and that the
print("activePlace current value is \(activePlace)")
returns the number of the line in the TableView
How could I solve this? thanks !
Here is the code in the TableView:
import UIKit
var places = [Dictionary<String,String>()]
var activePlace = -1
class TableViewController: UITableViewController {
func companyNameUpdatedAlert(title: String, error: String, indexPath: Int) {
let alert = UIAlertController(title: title, message: error, preferredStyle: UIAlertControllerStyle.Alert)
alert.addTextFieldWithConfigurationHandler { (textField) -> Void in
textField.placeholder = "Enter new text"
}
alert.addAction(UIAlertAction(title: "OK", style: .Default, handler: { (action) -> Void in
let lat = places[indexPath]["lat"]!
let lon = places[indexPath]["lon"]!
places.removeAtIndex(indexPath)
places.insert(["name" : alert.textFields![0].text!, "lat" : lat, "lon" : lon], atIndex: indexPath)
self.tableView.reloadData()
NSUserDefaults.standardUserDefaults().setObject(places, forKey: "places")
NSUserDefaults.standardUserDefaults().synchronize()
}))
self.presentViewController(alert, animated: true, completion: nil)
}
override func tableView(tableView: UITableView, editActionsForRowAtIndexPath indexPath: NSIndexPath) -> [UITableViewRowAction]? {
let changeText = UITableViewRowAction(style: UITableViewRowActionStyle.Default, title: "Change text" , handler: { (action:UITableViewRowAction, indexPath:NSIndexPath) -> Void in
self.companyNameUpdatedAlert("Update text", error: "enter text below", indexPath: indexPath.row)
})
let deleteAction = UITableViewRowAction(style: UITableViewRowActionStyle.Default, title: "Delete" , handler: { (action:UITableViewRowAction, indexPath:NSIndexPath) -> Void in
places.removeAtIndex(indexPath.row)
tableView.reloadData()
NSUserDefaults.standardUserDefaults().setObject(places, forKey: "places")
NSUserDefaults.standardUserDefaults().synchronize()
})
return [changeText, deleteAction]
}
override func viewDidLoad() {
//save start
if NSUserDefaults.standardUserDefaults().objectForKey("places") != nil {
places = NSUserDefaults.standardUserDefaults().objectForKey("places") as! [Dictionary]
//test
NSUserDefaults.standardUserDefaults().setObject(places, forKey: "places")
NSUserDefaults.standardUserDefaults().synchronize()
//save stop
super.viewDidLoad()
if places.count == 1 {
places.removeAtIndex(0)
places.append(["name":"go to map to add location","lat":"90","lon":"90"])
}
if NSUserDefaults.standardUserDefaults().objectForKey("places") != nil {
places = NSUserDefaults.standardUserDefaults().objectForKey("places") as! [Dictionary]
}
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
return 1
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return places.count
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as UITableViewCell
cell.textLabel?.text = places[indexPath.row]["name"]
return cell
}
override func tableView(tableView: UITableView, willSelectRowAtIndexPath indexPath: NSIndexPath) -> NSIndexPath? {
activePlace = indexPath.row
return indexPath
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "newPlace" {
activePlace = -1
}
}
override func viewWillAppear(animated: Bool) {
tableView.reloadData()
}
}
and here is the code in the viewController ( mapView)
if activePlace == -1 {
manager.requestWhenInUseAuthorization()
manager.startUpdatingLocation()
} else {
print("activePlace current value is \(activePlace)")
let latitude = NSString(string: places[activePlace]["lat"]!).doubleValue
let longitude = NSString(string: places[activePlace]["lon"]!).doubleValue
let coordinate = CLLocationCoordinate2DMake(latitude, longitude)
let latDelta:CLLocationDegrees = 0.01
let lonDelta:CLLocationDegrees = 0.01
let span:MKCoordinateSpan = MKCoordinateSpanMake(latDelta, lonDelta)
let region:MKCoordinateRegion = MKCoordinateRegionMake(coordinate, span)
self.Map.setRegion(region, animated: true)
let annotation = MKPointAnnotation()
annotation.coordinate = coordinate
annotation.title = places[activePlace]["name"]
self.Map.addAnnotation(annotation)
print("activePlaces current value is (activePlaces)")

Answer 1

First of all, You can create custom class, container. Like UserData with required information like description and location. Second, You have, for free from framework, a container for location CLLocationCoordinate2D, use it. If You will have just array of simple objects, it will be easier to read, find bugs and maintain application.
Your error simply says that element of array that You are trying to get is nil. Remember that in Swift Arrays, Dictionaries and other containers are passed via value, not via reference, because they are STRUCTS!
And Your problem is in prepareForSegue, why You are not passing selected item here to destinationViewController? You should do that.
P.S. Do not use NSUserDefaults.standardUserDefaults() to store user data. You can use CoreData instead, it is pretty simple to use. You need just a little extra code in AppDelegate and some changes in TableView.

Answer 2

The exclamation mark means: Dear compiler, I have an optional value. I am absolutely sure that it isn't nil. Should I be wrong, and should that optional value be nil when you unwrap it even though I was sure it isn't, then please crash and give me a fatal error "unexpectedly found nil while unwrapping optional value".
That's what you tell the compiler, and that's what you got. Where Objective-C lets you get away with things and maybe create strange behaviour, Swift doesn't.
Learn about "if let", guard statements, and in general read a good book about Swift.