iPhone Development: nil userInfo when receiving a notification - iphone

Question

I post the notifications like this in an operation:
DownloadStatus * status = [[DownloadStatus alloc] init];
[status setMessage: #"Download started"];
[status setStarted];
[status setCompleteSize: [filesize intValue]];
[userInfo setValue:status forKey:#"state"];
[[NSNotificationCenter defaultCenter]
postNotificationName:[targetURL absoluteString]
object:nil userInfo:userInfo];
[status release];
DownloadStatus is an object that contains some information abou the download that is being currently downloaded. userInfo is a property of the object that has been initialized in the init part and is kept for the complete duration of the operation. It is created so:
NSDictionary * userInfo = [NSDictionary dictionaryWithObject:targetURL
forKey:#"state"];
"targetURL" is a NSString, I use this just to make sure everything is working fine. When I receive the event - I registered like this:
[[NSNotificationCenter defaultCenter]
addObserver:self selector:#selector(downloadStatusUpdate:)
name:videoUrl
object:nil];
Here "videoUrl" is a string that contains the url being downloaded, so that I will receive notification about an url I'm waiting to see downloaded.
The selector is implemented like this:
- (void) downloadStatusUpdate:(NSNotification*) note {
NSDictionary * ui = note.userInfo; // Tried also [note userInfo]
if ( ui == nil ) {
DLog(#"Received an update message without userInfo!");
return;
}
DownloadStatus * state = [[ui allValues] objectAtIndex:0];
if ( state == nil ) {
DLog(#"Received notification without state!");
return;
}
DLog(#"Status message: %#", state.message);
[state release], state = nil;
[ui release], ui = nil; }
But this selector always receives a null userInfo. What am I doing wrong?
MrWHO

Answer 1

One way or another, you seem to be initialising your userInfo object incorrectly. The line as given:
NSDictionary * userInfo = [NSDictionary dictionaryWithObject:targetURL
forKey:#"state"];
Would create an autoreleased NSDictionary and store it to a local variable. The value would not be propagated up to your member variable.
Supposing that's a snippet, followed by e.g.
self.userInfo = userInfo;
to assign the local to the member, retaining it at the same time, then your code should generate an exception at this line:
[userInfo setValue:status forKey:#"state"];
Since it attempts to mutate an immutable object. It's therefore much more likely that the value of userInfo isn't stored and you're messaging nil at that point.
So, I would think that — assuming you have userInfo declared as a 'retain' type property, you want to replace:
NSDictionary * userInfo = [NSDictionary dictionaryWithObject:targetURL
forKey:#"state"];
With:
self.userInfo = [NSMutableDictionary dictionaryWithObject:targetURL
forKey:#"state"];