iPhone: IBAction Causes "Unrecognized Selector Sent to Instance" Error

Question

I'm working on my first real iPhone app, a simple To-Do list application to help me organize stuff, except I'm getting an "unrecognized selector sent to instance 0x".

Specifically:

2010-02-20 14:30:09.200 ToDoApp[88562:20b] *** -[NSCFDictionary switchViews:]: unrecognized selector sent to instance 0x3d22de0

2010-02-20 14:30:09.201 ToDoApp[88562:20b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[NSCFDictionary switchViews:]: unrecognized selector sent to instance 0x3d22de0'

I've looked around and figured out that it might be a connection problem in IB, but I'm new to this whole connecting thing (man, I wish they supported Java or Python), so here's how it's laid out. I've got 3 classes, a SwitchViewController, a MainScreenViewController, and a ToDoListViewController. When I hit a button on MainScreenViewController, I trigger the "switchViews" function that's throwing this problem. They way I've got it set up is that the button (a UIBarButtonItem) has the "sentAction" go to switchViews. This ViewButton has its reference outlet as a IBOutlet in SwitchViewController.

So here's the .h for SVC:

#import <UIKit/UIKit.h>

@class MainScreenViewController;
@class ToDoListViewController;
@class EditViewController;

#define kMinimumGestureLength 25
#define kMaximumVariance 5

@interface SwitchViewController : UIViewController {
 MainScreenViewController *mainScreenViewController;
 ToDoListViewController *toDoListViewController;
 EditViewController *editViewController;
 IBOutlet UIBarButtonItem *viewButton;
 CGPoint gestureStartPoint;
}

@property (retain, nonatomic) MainScreenViewController *mainScreenViewController;
@property (retain, nonatomic) ToDoListViewController *toDoListViewController;
@property (retain, nonatomic) EditViewController *editViewController;
@property (retain, nonatomic) IBOutlet UIBarButtonItem *viewButton;
@property CGPoint gestureStartPoint;
-(IBAction)switchViews:(id)sender;  

And for the switchViews function:

-(IBAction) switchViews:(id)sender
{
 NSLog(@"Switching views");
 if(self.toDoListViewController.view.superview == nil){
  if(self.toDoListViewController ==nil){
   ToDoListViewController *toDoVC = [[ToDoListViewController alloc]     initWithNibName:@"ToDoListView" bundle:nil];
   self.toDoListViewController = toDoVC;
   //[toDoVC release];
  }
  [mainScreenViewController.view removeFromSuperview];
  [self.view insertSubview:toDoListViewController.view atIndex:0];
 }
 else{
  if(self.mainScreenViewController == nil){
   MainScreenViewController *mainController =     [[MainScreenViewController alloc] initWithNibName:@"MainScreenView" bundle:nil];
   self.mainScreenViewController = mainController;
   //[mainController release];
  }
  [toDoListViewController.view removeFromSuperview];
  [self.view insertSubview:mainScreenViewController.view atIndex:0];
 }
}

So in short, I'm totally lost, and this is really frustrating. Anyone have any advice, or need any more code?

Answer 1

We just ran into the same problem. It seems we released the ViewController object in the AppDelegate and then our nib view tried to invoke an IBAction (on the view controller). Half the time we were getting "EXC_BAD_ACCESS" (aka messaging a released object), and half the time we were getting "unrecognized selector sent to instance" of NSCFString, NSCFArray, all sorts of things (aka messaging an area of memory now taken up by a different object).

Just check your ViewController hasn't been released.