NSNotificationCenter selector won't work with its NSNotification - objective-c

Question

I'm working on a Cocoa project with some C in it (I know, objc contains C...) and am trying to understand NSNotificationCenters. Here's the situation:
I have a struct declared as typedef struct {/*code here*/} structName;
In my - (id)init method, I have
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(selName:) name:#"notName" object:nil];
I have a callback function:
int callback(/*args*/) {
structName *f = ...
NSAutoreleasePool *autoreleasepool = [[NSAutoreleasePool alloc] init];
[[NSNotificationCenter defaultCenter] postNotificationName:#"notName" object:[[NSValue valueWithPointer:f] retain]];
[autoreleasepool release];
}
And then for my selector:
- (void)selName:(NSNotification *)note
{
NSLog(#"here");
NSLog(#"note is %#", note);
}
Now, if I comment out that second NSLog, everything seems to work (i.e. "here" is printed). But if I leave it in, nothing about the NSNotification seems to work. But this seems to defeat the purpose of the object, userInfo, etc. of the NSNotification.
What am I doing wrong and how can I fix it so I can have access to my structName f?
#Nathan
Okay, so now I have
NSDictionary *dict = [NSDictionary dictionaryWithObject:[NSValue valueWithPointer:f] forKey:#"fkey"];//f, not &f. I had a typo in the OP which I fixed.
[[NSNotificationCenter defaultCenter] postNotificationName:#"notName" object:nil userInfo:[dict retain]];
...but the problem remains. Any chance this has to do with the typo I fixed?
Edit:
The problem continues even with changing the two lines above to
[[NSNotificationCenter defaultCenter] postNotificationName:#"notName" object:nil userInfo:[NSDictionary dictionaryWithObject:[NSData dataWithBytes:f length:sizeof(structName)] forKey:#"fkey"]];

Answer 1

Works for me. What are you doing differently?

Answer 2

You should be using +notificationWithName:object:userInfo: not +notificationWithName:object:.
The object parameter is the object sending the notification. Normally this would be self for an object posting the notification but since your calling this from a C function it should be nil.
The userInfo parameter is an NSDictionary so add the NSValue to a dictionary and send that.
Then in your selName: method get the -userInfo dict from the NSNotification and pull your info out from there.
Note: You are creating a leak by retaining the NSValue when you shouldn't.
Edit:
How long does the struct exist? NSValue will not copy the contents of the pointer so maybe it's being deallocated? Try using NSData's dataWithBytes:length: instead.
Also make sure to check the console for runtime errors (in Xcode:Run > Console).
And you do not need to retain dict. You may want to (re)read the Cocoa memory management docs.

Answer 3

NSValue needs a pointer to your struct, not the struct itself:
[NSValue valueWithPointer:&f]

Answer 4

You said it worked if you comment out the second NSLog. And that second NSLog appears to be incorrect:
- (void)selName:(NSNotification *)note
{
NSLog(#"here");
NSLog(#"note is %#", note);
}
%# format is to print an NSString but "note" is not a NSString, it's an NSNotification object. NSNotification has a name attribute that returns an NSString. Try changing the second NSLog to this:
NSLog(#"note is %#", [note name]);

Answer 5

Instead, you can use the following:
- (void)selName:(NSNotification *)note
{
NSLog(#"here");
NSLog(#"note is %#", [note userInfo]);
}