I am making my first XCode project and I want to make an app where you can click on a tableviewcell and then you can see are directed to the next detailpage where the location is on the map. The problem is that I get a thread when i run the app:
Fatal error: Unexpectedly found nil while unwrapping an Optional value
and in my output i see that (MKMapView!) nil is.
This is my code on my MapViewController (the detailpage where the map is supposed to be)
import UIKit
import MapKit
class MapViewController: UIViewController, MKMapViewDelegate{
#IBOutlet weak var mijnMap: MKMapView!
var currentDetail: Parking? {
didSet {
showInfoDetail()
}
}
override func viewDidLoad() {
super.viewDidLoad()
}
func showInfoDetail() {
if let detail = currentDetail {
let coordinaat = CLLocationCoordinate2D(latitude: CLLocationDegrees(detail.latitude)
, longitude: CLLocationDegrees(detail.longitude))
MKMapPointForCoordinate(coordinaat)
mijnMap.centerCoordinate = coordinaat
mijnMap.region = MKCoordinateRegionMakeWithDistance(coordinaat, 1000, 1000)
let parkingAnnotation = MKPointAnnotation()
parkingAnnotation.coordinate = coordinaat
parkingAnnotation.title = detail.title
parkingAnnotation.subtitle = detail.city
mijnMap.addAnnotation(parkingAnnotation)
}
}
}
I get the threat on this line mijnMap.centerCoordinate = coordinaat
Can someone help me with this? Thanks!
The problem is that because of didSet in
var currentDetail: Parking? {
didSet {
showInfoDetail()
}
}
when you try to set currentDetail from another VC the call to method showInfoDetail triggers and this happen before the VC is presented which means prior to view loading resulting in a crash as all IBOutlets are not yet been initialized , so delay the call to it in viewDidAppear or check the map before usage
var currentDetail: Parking? {
didSet {
if mijnMap != nil {
showInfoDetail()
}
}
}
Note in second option you have at call showInfoDetail in viewDidLoad / viewDidAppear , I'm not suggesting removing didSet as you may want to change that string value in MapViewController and trigger the same function every change
Related
I am creating a macOS app on Xcode 9.2 and i can't figure out why after the views hierarchy is created in viewDidLoad(), i can't use anymore the IBOutlet which is referencing the view in the StoryBoard.
I have found similar question, where they suggest to save the view that i want to update, as a variable, when i am in viewDidLoad() so i can use it later; if so what is the advantage of using an IBOutlet?
Can someone pls explain how to update in this case the content of the PDFView outside viewDidLoad() without getting nil?
The AppDelegate
import Cocoa
#NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate {
// MARK: - Properties
var filePath: URL?
var result: Int?
var fileObject: Data?
// MARK: - Outlets
#IBOutlet weak var openFileMenuItem: NSMenuItem!
// MARK: - App Life Cycle
func applicationDidFinishLaunching(_ aNotification: Notification) {
// Insert code here to initialize your application
}
func applicationWillTerminate(_ aNotification: Notification) {
// Insert code here to tear down your application
}
// MARK: - My Functions
#IBAction func openFile(_ sender: NSMenuItem) {
//Get the window of the app
var window = NSApplication.shared.mainWindow!
// Create NSOpenPanel and setting properties
let panel = NSOpenPanel()
panel.title = "Select file"
panel.allowsMultipleSelection = false;
panel.canChooseDirectories = false;
panel.canCreateDirectories = false;
panel.canChooseFiles = true;
// Filtering file extension
let fileTypes: [String] = ["pdf"]
panel.allowedFileTypes = fileTypes
// Showing OpenPanel to the user for selecting the file
panel.beginSheetModal(for: window) {
(result) in
if result.rawValue == NSFileHandlingPanelOKButton {
// Getting url of the file
self.filePath = panel.urls[0]
print(self.filePath)
// Creating Data Object of the file for creating later the PDFDocument in the controller
do {
if let fileData = self.filePath {
self.fileObject = try Data.init(contentsOf: self.filePath!)
print("\(self.fileObject) ")
}
} catch let error as NSError {
print("Error with file Data Object: \(error)")
}
// Getting the mainViewController
let storyboard = NSStoryboard(name: NSStoryboard.Name(rawValue: "Main"), bundle: nil)
let mainController = storyboard.instantiateController(withIdentifier: NSStoryboard.SceneIdentifier(rawValue: "mainViewControllerID")) as! MainViewController
// Appdelegate call function of mainViewController to update the content of PDFView
mainController.showPdfDocument(fileData: self.fileObject!)
}
}
}
}
The MainViewController:
import Foundation
import Quartz
class MainViewController: NSViewController {
// MARK: - Property
var pdfdocument: PDFDocument?
// MARK: - Outlets
#IBOutlet var mainView: NSView!
#IBOutlet var pdfView: PDFView!
// MARK: - App Life Cycle
override func viewDidLoad() {
super.viewDidLoad()
}
override var representedObject: Any? {
didSet {
// Update the view, if already loaded.
}
}
// MARK: - My Functions
func showPdfDocument(fileData: Data) {
print("appdelegate calling showPdfDocument on mainViewController " )
pdfdocument = PDFDocument(data: fileData)
pdfView.document = pdfdocument
}
}
The Error I Am Getting:
fatal error: unexpectedly found nil while unwrapping an Optional value
I solved the problem with the current code in the AppDelegate. Basically i am using the contentViewController to update the PDFView but i don't know if this is a good practice because i should update the PDFView with its own controller and not with the one of the window.
in the openFile function of the AppleDelegate:
let storyboard = NSStoryboard(name: NSStoryboard.Name(rawValue: "Main"), bundle: nil)
let mainViewController = NSApplication.shared.mainWindow?.contentViewController as! MainViewController
mainViewController.showPdfDocument(fileData: self.fileObject!)
Reading from the Apple documentation at this link (https://developer.apple.com/documentation/appkit/nswindow/1419615-contentviewcontroller) it says 'Directly assigning a contentView value clears out the root view controller.'. Should I programmatically assign my mainView to the contentView to automatically set my mainViewController as the initial controller?
I have also found that i can set my controller as the initial controller from IB as you can see form this image:
The ideal thing i want to do is to leave the contentViewController as the initial viewController (the default setting in IB) and then instantiate my mainViewController to update the pdfView. The problem is that with instantiation, the new viewController has everything to nil(IBOutlet, vars etc..). Is it the downcasting from contentViewController to mainViewController a good approach to achieve this task?
When dialing with CocoaTouch, it often happens that UIView(Controller) subclass properties can't be initialized in init method (ex. we need view already loaded), but logically they are non-optional and even non-var. In such cases the property must be optional to compile without errors, what looks pretty ugly - the code is fulfilled with !.
Is there any way to solve this problem? I would imagine some deferred initialization. Perfectly if such property can compile without initial value and crash at runtime if it's accessed prior to be initialized.
Some code sample to describe the issue:
class MyVC: UIViewController {
#IBOutlet var someLabel: UILabel!
let viewBasedParam: CustomClass // how to keep it non-optional if it can be initialized after view has been loaded?
override func viewDidLoad() {
super.viewDidLoad()
self.viewBasedParam = CustomClass(self.someLabel.text)
}
}
P.S. CustomClass can't have default initializer, because it requires data from view.
In your MyVC you can have a convenience init method where you can initialize the let variables. Try this and let me know if it works for you:
class MyVC: UIViewController {
let viewBasedParam: CustomClass
convenience init() {
self.init(nibName:nil, bundle:nil)
self.viewBasedParam = CustomClass(self.someLabel.text)//else just initialize with empty string here and then assign actual value in viewDidLoad
}
}
As far as I've discovered the workaround solution may be following:
class MyVC: UIViewController {
#IBOutlet var someLabel: UILabel!
private var _viewBasedParam: CustomClass? = nil
var viewBasedParam: CustomClass {
get { return self._viewBasedParam! } // always unwrap private optional
set { self._viewBasedParam = newValue }
}
override func viewDidLoad() {
super.viewDidLoad()
self.viewBasedParam = CustomClass(self.someLabel.text)
}
}
I am trying to implement UITapGestureRecognizer, Idea is that on tap of label I will get a pop up displaying the number to make call and it should come up with pop up alert saying call or cancel!!
Code I've written worked for me in 3 to 4 places but I am stuck at one point
In this screen I have a tableview with prototype cells grouped type here, please check this Image:
Link For Image
Third Cell
Now If I am Tapping 065668982 I have canOpenURL: failed for URL: "telprompt://065668982" - error: "This app is not allowed to query for scheme telprompt" which actually works on iPhone not on simulator and it pulls to call which is working fine.
Second Cell
If I am Tapping 065454858 I have canOpenURL: failed for URL: "telprompt://065668982" - error: "This app is not allowed to query for scheme telprompt" which actually works on iPhone not on simulator and it pulls to call which is working fine.
first Cell
But for first one it never works and end up with fatal error: unexpectedly found nil while unwrapping an Optional value
NOTE : I am Getting phone Number from an API and append the data in view controller to UITableViewCell.
I Hope I make sense, Thanks in advance for any help also if I am not clear please comment below
Here is my code:
import UIKit
import Foundation
class XyzTableViewCell: UITableViewCell
{
#IBOutlet weak var phoneNumber: UILabel!
var touchContact : String = ""
var myCell: MyCellData! {
didSet {
self.updateUI()
}
}
func updateUI()
{
touchContact = vicarCell.phone_no
//Tap Gesture
tapGestureAddonView()
}
//MARK:- Tap to Call and Open Email
func tapGestureAddonView(){
let contacttap = UITapGestureRecognizer(target: self, action:("contactTapped"))
contacttap.numberOfTapsRequired = 1
phoneNumber!.userInteractionEnabled = true
phoneNumber!.addGestureRecognizer(contacttap)
}
func contactTapped() {
// do something cool here
print("contactTapped")
print(touchContact)
dispatch_async(dispatch_get_main_queue())
{
if UIApplication.sharedApplication().canOpenURL(NSURL(string: "telprompt://\(self.touchContact)")!){
UIApplication.sharedApplication().openURL(NSURL(string: "telprompt://\(self.touchContact)")!)
}
else{
//showAlert("Info",message: "Your device could not called" ,owner: self)
}
}
}
The issues: 1) you should add gesture only once 2) you should check NSURL for nil. Let me assume that you use storyboard and improve your code a bit
class XyzTableViewCell: UITableViewCell
{
#IBOutlet weak var phoneNumber: UILabel!
var touchContact : String = ""
var myCell: MyCellData! {didSet {self.updateUI()}}
func updateUI() {
touchContact = myCell.phone_no // did you mean myCell instead vicarCell?
}
override func awakeFromNib() {
super.awakeFromNib()
tapGestureAddonView()
}
func tapGestureAddonView(){
let contacttap = UITapGestureRecognizer(target: self, action: #selector(contactTapped))
contacttap.numberOfTapsRequired = 1
phoneNumber!.userInteractionEnabled = true
phoneNumber!.addGestureRecognizer(contacttap)
}
func contactTapped() {
print("contactTapped")
print(touchContact)
if touchContact.isEmpty {return}
guard let url = NSURL(string: "telprompt://\(touchContact)") else {
print("url string invalid")
return
}
dispatch_async(dispatch_get_main_queue())
{
if UIApplication.sharedApplication().canOpenURL(url){
UIApplication.sharedApplication().openURL(url)
} else{
//showAlert("Info",message: "Your device could not called" ,owner: self)
}
}
}
}
I have a UILabel inside a modelviewcontroller.
What i want to do is change its text on a certain point of my code. The problem is it works in the first point and stops working on the second one, throwing the following error:
unexpectedly found nil while unwrapping an Optional value
I found other questions on the same error but those solutions are not working for me. Maybe I am doing something wrong with the optionals.
Here is the code of my model view controller:
import UIKit
class CheckInViewController: UIViewController {
#IBOutlet weak var test: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewDidAppear(animated: Bool) {
print("Appeared")
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let vc = storyboard.instantiateViewControllerWithIdentifier("scanViewController") as! ScanViewController
test.text = "Here it works" // FIRST POINT WORKS AND CHANGES THE LABEL
if let qrCode = vc.qrCode{ // vc.qrCode IS AN OPTIONAL
qrRead(qrCode)
vc.qrCode = nil
}
}
func qrRead(qrCode: String) {
print(qrCode)
test.text = "Here it doesnt work" // HERE IT STOPS WORKING
}
You are setting the vc.qrCode to nil directly after passing it to the func qrRead(qrCode: String) function.
Remove this line: vc.qrCode = nil and check if the error persists.
If it does not, as I suspect, nil the var out elsewhere.
Remember using if let, you actually access the underlying instance, not a copy.
As such, when you set vc.qrCode to nil, you are ALSO setting qrCode to nil which causes issues when you try to print it in the qrRead function
Example:
class Person {
}
var a:Person? = Person()
if let some = a
{
print(unsafeAddressOf(some))
print(unsafeAddressOf(a!))
}
Prints:
0x0000000005011ed0
0x0000000005011ed0
Which shows they are the same instance in memory.
When I receive in my Bluetooth class (new) values from my device, then I call a delegate. So the Bluetooth class is running in the background.
My protocol is simple:
protocol RefreshPositionInDrive {
func changingValue(latitude: Double, longitude: Double)
}
In my UIViewController I initialize a map. When I worked at the beginning without delegates this code works fine.
func initializeMapResolution() {
let regionRadius: CLLocationDistance = 1000
let initialLocation = CLLocation(latitude: 50.910349, longitude: 8.066895)
let coordinateRegion = MKCoordinateRegionMakeWithDistance(initialLocation.coordinate,
regionRadius * 1.5, regionRadius * 1.5)
MapDrive.setRegion(coordinateRegion, animated: true)
MapDrive.delegate = self
}
My method from my protocol:
func changingValue(latitude: Double,longitude: Double) {
print("THE NEW COORDINATES \(latitude) \(longitude)")
if self.MapDrive == nil {
print("Is nil")
} else {
updateTheMap()
}
}
Output:
THE NEW COORDINATES 25.012x 16.992
Is nil
But I don't understand that. I initialize my map first. After that the changingValue is called. How can be the MapDrive nil?
I tested the code without delegates, just with some fix coordinates in my UIViewController and the annotation appears.
(I'm working the first time with delegates.)
EDIT
I was indistinctly: My MapDrive:
#IBOutlet weak var MapDrive: MKMapView!
So I can't instantiate like you mean or?
You'll want to reference a MapDrive instance to the UIViewController, your MapDrive is probably released when your function ends.
class UIViewController {
var mapDrive = MapDrive()
func initializeMapResolution() {
// Instantiate map drive, assign it to self.mapDrive
//then assign the delegate of the property on self.
self.mapDrive.delegate = self
}
}