How to use a parameterized method with NSNotificationCenter?

Question

I want to pass a dict to the processit method. But as soon as I get access to the dictionary, I get EXC__BAD_INSTRUCTION.

NSNotificationCenter *ncObserver = [NSNotificationCenter defaultCenter]; [ncObserver addObserver:self selector:@selector(processit:) name:@"atest" object:nil]; NSDictionary *dict = [[NSDictionary alloc] initWithObjectsAndKeys:@"testing", @"first", nil]; NSString *test = [dict valueForKey:@"first"]; NSNotificationCenter *ncSubject = [NSNotificationCenter defaultCenter]; [ncSubject postNotificationName:@"atest" object:self userInfo:dict]; 

In the recipient method:

 - (void) processit: (NSDictionary *)name{ NSString *test = [name valueForKey:@"l"]; //EXC_BAD_INSTRUCTION occurs here NSLog(@"output is %@", test); } 

Any suggestions on what I'm doing wrong?

Answer 1

You will get an NSNotification object, not an NSDictionary in the notification callback.

Try the following:

 - (void) processit: (NSNotification *)note { NSString *test = [[note userInfo] valueForKey:@"l"]; NSLog(@"output is %@", test); } 

Answer 2

Amrox is absolutely right.

You can also use Object (instead of userInfo) for the same as below:

 - (void) processit: (NSNotification *)note { NSDictionary *dict = (NSDictionary*)note.object; NSString *test = [dict valueForKey:@"l"]; NSLog(@"output is %@", test); } 

In this case, your postNotificationName: object will look like this:

 [[NSNotificationCenter defaultCenter] postNotificationName:@"atest" object:dict]; 

Answer 3

You will get an NSNotification object, not an NSDictionary in the notification callback.

• (void) processit: (NSNotification *) note {

  NSDictionary dict = (NSDictionary) note.object;

  NSString * test = [dict valueForKey: @ "l"];

  NSLog (exit "@" -% @ ", test);}