"unrecognized selector sent to instance" when selector is in other file - ios

Question

Here is the problematic ViewController class.
class ViewController: UIViewController {
#IBOutlet weak var photoSelectActionSheet: UIButton!
#IBOutlet weak var selectedImageView: UIImageView!
var imagePicker: UIImagePickerController!
var selectedImage: UIImage? = ni
var iCloud = ICloud() // see below for code of that file
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
// Must use this system to check each time the view appears.
// This is checked each time so if user goes into settings and come back in same session
// then this will be updated => viewDidLoad is cached and not reloaded each time.
NotificationCenter.default.addObserver(
self,
selector:#selector(ICloud.checkIfUserIsLoggedInIcloud), // PROBLEM IS HERE
name: UIApplication.didBecomeActiveNotification,
object: nil)
}
// more code not shown
}
Problem is in viewWillAppear: the notification center calls a selector that is in an other Model file ICloud.swift:
import UIKit
import CloudKit
class ICloud {
var isLoggedInIcloud: Bool? = nil
var userIcloudId: String? = nil
func getUserIcloudId() {
// Run this only if user is logged into icloud, and we don't have yet its iCloud id.
if isLoggedInIcloud ?? false && userIcloudId == nil {
CKContainer.default().fetchUserRecordID(completionHandler: { (recordId, error) in
if let id = recordId?.recordName {
print("userIcloudId set to: " + id)
self.userIcloudId = id
}
else if let error = error {
print(error.localizedDescription)
}
})
}
}
#objc func checkIfUserIsLoggedInIcloud() {
// Check if user is logged into iCloud
CKContainer.default().accountStatus { accountStatus, error in
if accountStatus == .available {
self.isLoggedInIcloud = true
print("isLoggedInIcloud set to true")
self.getUserIcloudId()
return
}
print("User is not logged into icloud")
}
}
}
I expected "ICloud.checkIfUserIsLoggedInIcloud" passed in selector to work. It doesn't:
2020-07-01 11:46:12.931419+0200 QDog[53348:3422745] -[QDog.ViewController checkIfUserIsLoggedInIcloud]: unrecognized selector sent to instance 0x7fcad5f0c1d0
2020-07-01 11:46:12.938567+0200 QDog[53348:3422745] *** Terminating app due to uncaught exception
If I add back the functions and variables from ICloud.swift directly into the ViewController file and pass to the selector "checkIfUserIsLoggedInIcloud" it WILL WORK properly.
I wanted to put all icloud code into a separate model file for separation of concerns and to make the code more clear.
Question is: why does 'ICloud.checkIfUserIsLoggedInIcloud' passed as selector doesn't work? And how to make this work with ICloud code in its own file, and not in ViewController file?

Answer 1

According to the documentation, the first parameter should be the observer, which in your case you're pointing to self.
In this case, self is your ViewController, which doesn't have the method checkIfUserIsLoggedInIcloud. In order to make it work, as an observer, you need to pass the property iCloud instead of self.