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

I'm going to guess the problem is in your nib file.

The error means that upon clicking the button, the button tries to send a message/method-call of switchView to an NSDictionary object which of course has no such method. The error then lays in where the buttons action is pointed.

Check the nib for this view. Look at the File Owner and check the class assigned to it. Make sure it is SwitchViewController and not a dictionary for some reason. If the File Owner property is set to a dictionary class it will load a dictionary and try to send the action method it to it.

Answer 2

Okay, got the solution pointed out to me. Should have had it routed through FirstResponder (I ... really don't understand why that works, but at this point I'm just happy it works.)

I'm not sure how first responder works anyways (none of the books I have really mention it), but it... works? If someone wants to give me a rundown, that'd be useful... but this question has been answered.