Unrecognized selector sent to class uncaught exception of type NSException / NSInvalidArgumentExce-CodePudding

I'm still crashing my app with the UIBarButtonItem: I've tried 3 several ways I found here in previous topics, and none of them have worked out. I'm new to Swift and I really don't know what could be causing the problem, before it worked just fine...

The 3 several ways I tried, which 1 is the original code:

1) let btnDone = UIBarButtonItem(barButtonSystemItem: .done, target: MyViewController.self, action: #selector(onBtnDoneTap))

@objc private func onBtnDoneTap() { code to be executed on tap... }

2) let btnDone = UIBarButtonItem(barButtonSystemItem: .done, target: MyViewController.self, action: #selector(onBtnDoneTap(sender:)))

@objc private func onBtnDoneTap(sender: UIBarButtonItem) { code to be executed on tap... }

3) let btnDone = UIBarButtonItem(barButtonSystemItem: .done, target: MyViewController.self, action: #selector(onBtnDoneTap(_:)))

@objc private func onBtnDoneTap(_ sender: UIBarButtonItem) { code to be executed on tap... }

All crashed on the following line:

UIApplicationMain(CommandLine.argc, CommandLine.unsafeArgv, nil, NSStringFromClass(appDelegateClass))

Thread 1: " [App.MyViewController onBtnDoneTap]: unrecognized selector sent to class 0x1051c38b0"

With the following errors in the output window:

[13122:7952368] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: ' [App.MyViewController onBtnDoneTap]: unrecognized selector sent to class 0x1051c38b0'

libc abi: terminating with uncaught exception of type NSException dyld4 config: DYLD_LIBRARY_PATH=/usr/lib/system/introspection DYLD_INSERT_LIBRARIES=/Developer/usr/lib/libBacktraceRecording.dylib:/Developer/usr/lib/libMainThreadChecker.dylib:/Developer/Library/PrivateFrameworks/DTDDISupport.framework/libViewDebuggerSupport.dylib

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: ' [App.MyViewController onBtnDoneTap]: unrecognized selector sent to class 0x1051c38b0' terminating with uncaught exception of type NSException (lldb)

Thanks for your help!

Changing the target to "self", causes a warning but the app doesn't explote anymore, I can live with the warnings as long it doesn't explote:

class MyViewController: UIViewController { let btnDone = UIBarButtonItem(barButtonSystemItem: .done, target: self, action: #selector(onBtnDoneTap)) }

Which now here appears the warning 'self' refers to the method ‘MyViewController.self', which may be unexpected

`extension MyViewController: UIPickerViewDelegate, UIPickerViewDataSource {

@objc private func onBtnDoneTap() {
    self.dummyTextField.resignFirstResponder()
    let selectedLanguage = self.selectedItem?.Languages?
    ...
}

CodePudding user response：

Instead of MyViewController.self as the action target, use self:

let btnDone = UIBarButtonItem(barButtonSystemItem: .done, target: self, action: #selector(onBtnDoneTap))

This means that the target is not the class MyViewController but a specific MyViewController instance.