"unrecognized selector sent to instance" error in Objective-C

Question

I created a button and added an action for it, but as soon as it invoked, I got this error:

-[NSCFDictionary numberButtonClick:]: unrecognized selector sent to instance
 0x3d03ac0 2010-03-16 22:23:58.811
 Money[8056:207] *** Terminating app
 due to uncaught exception
 'NSInvalidArgumentException', reason:'*** -[NSCFDictionary numberButtonClick:]:  unrecognized selector sent to instance 0x3d03ac0'

This is my code:

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
    if (self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]) {
        UIButton *numberButton = [UIButton buttonWithType:UIButtonTypeCustom];        
        numberButton.frame = CGRectMake(10, 435, 46, 38);
        [numberButton setImage:[UIImage imageNamed:@"one.png"] forState:UIControlStateNormal];
        [numberButton addTarget:self action:@selector(numberButtonClick:) forControlEvents:UIControlEventTouchUpInside];
        [self.view addSubview: numberButton]; 
    }
return self;
}

-(IBAction)numberButtonClick:(id)sender{
    NSLog(@"---");
}

Answer 1

My case: I forgot to set Home as Class in Storyboard. So basically in the ViewController with a button that was supposed to perform a segue the class wasn't connected to home.. Screenshot in the link

Answer 2

How to debug ‘unrecognized selector send to instance’

In most of the cases Xcode do not take us to the exact line where this issue happen. When app crash you won’t see the line of code that caused this, rather you will be taken to App delegate class, in which the error output may look like:

[UITableViewCellContentView image]: unrecognized selector sent to instance

or

[__NSDictionaryI objectAtIndex:] unrecognized selector sent to instance

or

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[TestApp.MyViewController viewDidLoad:]: unrecognized selector sent to instance 0xDABCDD'

How to find line of code causing this:

Go to breakpoint navigator. Click ‘+’ option. click ‘Exception Breakpoint’. An new widget like following will apear.

Add following condition block:

-[NSObject(NSObject) doesNotRecognizeSelector:]

You can also put breakpoint for all exception. Now run your code again. this time, breakpoint will trigger when this exception occurs.

WRITTEN BY: Prafulla Singh

Full explanition: https://prafullkumar77.medium.com/how-to-debug-unrecognized-selector-send-to-instance-402473bc23d

Answer 3

According to Apple, I needed to update an app that had been running fine for years. My app was originally written in Objective-C (well before Swift) and later (mostly) converted to Swift.

I tried many of the solution in this post. When I clicked on a button, instead of calling the handler

func willPause(_ sender: UIButton)
{
    pauseToggle()
}

I got the "unrecognized selector sent to instance" error.

What finally worked for me was adding "@objc" in front of the function

@objc func willPause(_ sender: UIButton)

Answer 4

In my case, in iOS 13, I only had to implement the whole function and selector calling parts put in to main thread.

Answer 5

OK LISTED UP! I'm VERY new to XCODE, had this problem, and figured it out! So if that sounds like you, here's the answer:

When you control + click and drag the button to your ViewController file (so you can code it), you will be asked to fill out the properties of the button in a popup.

The bottom of the popup (under Type) will say "SENDER".

YOU NEED TO CHANGE IT TO "NONE"

Answer 6

In my case, I was using NSNotificationCenter and was attempting to use a selector that took no arguments, but was adding a colon. Removing the colon fixed the problem.

When using a selector name, don't use a trailing colon if there are no arguments. If there's one argument, use one trailing colon. If there are more than one argument, you must name them along with a trailing colon for each argument.

See Adam Rosenfield's answer here: Selectors in Objective-C?

Answer 7

On my case I solved the problem after 2 hours :

The sender (a tabBar item) wasn't having any Referencing Outlet. So it was pointing nowhere.

Juste create a referencing outlet corresponding to your function.

Hope this could help you guys.

Answer 8

In my case:

My protocol definition

 @protocol MyProtocol

- (void)Method;

@end

and I forgot implements the delegate methods.

hope it could help someone.

Answer 9

My case was: collectionView inside a View

I was trying to add the gestureRecognizer in a config() method that I have wrote by myself. After some workaround i've found that I have simply to move the code inside the awakeFromNib().

override func awakeFromNib() {

   //other code

   let longPressGesture = UILongPressGestureRecognizer(target: self, action: #selector(handleLongGesture(gesture:)))
   self.collectionView.addGestureRecognizer(longPressGesture)
}

And it worked well.

I hope that this can help someone.

Answer 10

I had this after switching from Swift 2 to Swift 3. The description below is specific, but you can see the generic case of it covers a lot of possible errors.

I had a method called delete in my subclass of SKNode.

func delete(thing: SomeType) 

There is already a method delete on UIResponder, but my method (unintentionally) overloaded it, so it was working fine. Upgrading to Swift 3 changed it to:

func delete(_ thing: SomeType) 

Still working. But then I decided to Swift3ify it and made the parameter mandatory:

func delete(thing: SomeType)

which would have worked fine if I remembered to update the caller, but I didn't so now the caller is calling the no-parameter-name delete method in UIResponder with the wrong type of arguments.

This can obviously happen with any of the long list of of standard methods on SKNode (and probably UIView) that take Any as an argument and so will pass the compilation phase but then fall-over when called.

Answer 11

This happened to my because accidentally erase the " @IBAction func... " inside my UIViewcontroller class code, so in the Storyboard was created the Reference Outlet, but at runtime there was any function to process it.

The solution was to delete the Outlet reference inside the property inspector and then recreate it dragging with command key to the class code.

Hope it helps!

Answer 12

I also had the same issue.

I deleted my uibutton in my storyboard and recreated it .. now everything works fine.

Answer 13

I got this issue trying some old format code in Swift3,

let swipeRight = UISwipeGestureRecognizer(target: self, action: #selector(self.respond))

changing the action:"respond:" to action: #selector(self.respond) fixed the issue for me.

Answer 14

I had this problem with a Swift project where I'm creating the buttons dynamically. Problem code:

var trashBarButtonItem: UIBarButtonItem {
    return UIBarButtonItem(barButtonSystemItem: .Add, target: self, action: "newButtonClicked")
}

func newButtonClicked(barButtonItem: UIBarButtonItem) {
    NSLog("A bar button item on the default toolbar was clicked: \(barButtonItem).")
}

The solution was to add a full colon ':' after the action: e.g.

var trashBarButtonItem: UIBarButtonItem {
        return UIBarButtonItem(barButtonSystemItem: .Add, target: self, action: "newButtonClicked:")
    }

    func newButtonClicked(barButtonItem: UIBarButtonItem) {
        NSLog("A bar button item on the default toolbar was clicked: \(barButtonItem).")
    }

Full example here: https://developer.apple.com/library/content/samplecode/UICatalog/Listings/Swift_UIKitCatalog_DefaultToolbarViewController_swift.html

Answer 15

For me, it was a leftover connection created in interfacebuilder bij ctrl-dragging. The name of the broken connection was in the error-log

*** Terminating app due to uncaught exception 'NSInvalidArgumentException',
reason: '-[NameOfYourApp.NameOfYourClass nameOfCorruptConnection:]:
unrecognized selector sent to instance 0x7f97a48bb000'

I had an action linked to a button. Pressing the button crashed the app because the Outlet no longer existed in my code. Searching for the name in the log led me to it in the storyboard. Deleted it, and the crash was gone!

Answer 16

I got the issue too, and at last I found the solution for my issue.I was builded the controller's UI in storyboard , but the controller's UI did not relate its control to code, I use this code to init vc:

    UIStoryboard *sb = [UIStoryboard storyboardWithName:@"Me" bundle:nil];
    [sb instantiateViewControllerWithIdentifier:@"HeaderViewController"];

This code above will cause the issue, and after I changed the init code to this below, I resolved the problem:

HeaderViewController *head_vc = [[HeaderViewController alloc] init];

Answer 17

I had the same issue. The problem for me was that one button had two Action methods. What I did was create a first action method for my button and then deleted it in the view controller, but forgot to disconnect the connection in the main storyboard in the connection inspector. So when I added a second action method, there were now two action methods for one button, which caused the error.

Answer 18

Yet another slightly different solution/case.

I am using Xamarin and MvvmCross and I was trying to bind the UIButton to a ViewModel. I had the UIButton wired up to an Outlet and a TouchUpInside.

When Binding I only use the Outlet:

set.Bind (somethingOutlet).For ("TouchUpInside").To(vm => vm.Something);

All I had to do was remove the action (TouchUpInside) connection in XCode and that solved it.

P.S. I guess this is in its base all related to the previous answers and to @Chris Kaminski in particular, but I hope this helps someone...

Cheers.

Answer 19

Basics: Dynamic Invocation

The objective C is a dynamic language which invokes methods by looking at runtime for methods in classes. For example, if there is Class A including method DoSomething(arg1, arg2). If you try to call the method using correct arguments on an object of Class A everything will work fine. However, if the arguments are not passes properly, for example, you called the method with one argument only then the the run-time will treat this as a method call for a different method. Eventually, run-time will fail to find the method (DoSomething with one argument) and will through this exception "unrecognized selector sent to instance".

Solution

Please check what signature for @selector is expected. Usually it is, as you described in the code

-(IBAction)numberButtonClick:(id)sender{

Answer 20

..And now mine

I had the button linked to a method which accessed another button's parameter and that worked great BUT as soon I tried to do something with the button itself, I got a crash. While compiling, no error has been displayed.. Solution?

I failed to link the button to the file's owner. So if anyone here is as stupid as me, try this :)

Answer 21

I had the same error and I discovered the following:

When you use the code

[self.refreshControl addTarget:self action:@selector(yourRefreshMethod:) forControlEvents:UIControlEventValueChanged];

You may think it's looking for the selector:

- (void)yourRefreshMethod{
    (your code here)
}

But it's actually looking for the selector:

- (void)yourRefreshMethod:(id)sender{
    (your code here)
}

That selector doesn't exist, so you get the crash.

You can change the selector to receive (id)sender in order to solve the error.

But what if you have other functions that call the refresh function without providing a sender? You need one function that works for both. Easy solution is to add another function:

- (void)yourRefreshMethodWithSender:(id)sender{
    [self yourRefreshMethod];
}

And then modify the refresh pulldown code to call that selector instead:

[self.refreshControl addTarget:self action:@selector(yourRefreshMethodWithSender:) forControlEvents:UIControlEventValueChanged];

I'm also doing the Stanford iOS course on an older Mac that can't be upgraded to the newest version of Mac OSX. So I'm still building for iOS 6.1, and this solved the problem for me.

Answer 22

Happened to me because of conflicting constraint arguments.

Answer 23

My problem and solution was different and I thought I should post it here so that future readers can save their head from banging to the wall.

I was allocating different xib to same UIVIewController and even after searching everywhere I couldn't find how to correct it. Then I checked my AppDelegate where I was calling initWithNibName and can see that while copying the code, I changed the xib name, but forgot to change UIViewController class. So if none of the solution works for you, check your initWithNibName method.

Answer 24

OK, I have to chip in here. The OP dynamically created the button. I had a similar issue and the answer (after hours of hunting) is so simple it made me sick.

When using:

action:@selector(xxxButtonClick:)

or (as in my case)

action:NSSelectorFromString([[NSString alloc] initWithFormat:@"%@BtnTui:", name.lowercaseString])

If you place a colon at the end of the string - it will pass the sender. If you do not place the colon at the end of the string it will not, and the receiver will get an error if it expects one. It is easy to miss the colon if you are dynamically creating the event name.

The receiver code options look like this:

- (void)doneBtnTui:(id)sender {
  NSLog(@"Done Button - with sender");
}
 or
- (void)doneBtnTui {
  NSLog(@"Done Button - no sender");
}

As usual, it is always the obvious answer that gets missed.

Answer 25

In my case I was using a UIWebView and I passed a NSString in the second parameter instead of a NSURL. So I suspect that wrong class types passed to a functions can cause this error.

Answer 26

I'm currently learning iOS development and going through the "Beginning iOS6 Development" book by aPress. I was getting the same error in Chapter 10:Storyboards.

It took me two days to figure it out but found out I accidentally set the TableView cell's tag to 1 when I shouldn't have. For anyone else doing this book and receive a similar error I hope this helps.

I really hope future errors in my code are easier to find! hahaha. The debug error did nothing to push me in the right direction to figuring it out (or at least I'm too new to understand the debugger, lol).

Answer 27

The most obvious cause of this (included for completeness) is improperly casting a pointer and calling a method of the wrong class.

NSArray* array = [[NSArray alloc] init];
[(NSDictionary*)array objectForKey: key]; // array is not a dictionary, hence exception

Answer 28

In my case the function was not expecting an argument but the button was configured to send one causing the error. To fix this I had to rewire the event handler.

Here is my function:

Notice it contains no arguments.

Here is an image of my button configuration (right click on the button to view it):

Notice there are 3 event handlers.

To fix this I had to remove each of the event items since one of them was sending a reference to itself to the enterPressed function. To remove these items I clicked on the little x icon next to the name of each item until there were no items shown.

Next I had to reconnect the button to the event. To do this hold down the Control key and then drag a line from the button to the action. It should say "Connect Action". Note: I had to restart XCode for this to work for some reason; otherwise it only let me insert actions (aka create a new action) above or below the function.

You should now have a single event handler wired to the button event that passes no arguments:

This answer compliments the answer by @Leonard Challis which you should read as well.

Answer 29

Another possible solution: Add '-ObjC' to your linker arguments.

Full explanation is here: Objective-C categories in static library

I think the gist is: if the category is defined in a library you are statically linking with, the linker isn't smart enough to link in category methods. The flag above makes the linker link in all objective C classes and categories, not just ones it thinks it needs to based on analyzing your source. (Please feel free to tune or correct that answer. I'm knew to linked languages, so I'm just parroting here).

Answer 30

This also might happen when you want to set a property from a ControllerA to a public property inside a custom ControllerB class and you haven't set the "Custom Class" inside the identity inspector in storyboards yet.