Question

I need to post a notification using postNotificationName:object:userInfo: method, and I’m passing a custom class FileItem in as userInfo so I can obtain it on the other end. Should I use autorelease like this

FileItem *item = [[[FileItem alloc] init] autorelease];
[[NSNotificationCenter defaultCenter] postNotificationName:@"dataReceived" object:self userInfo:item];
[item release];

or can I just alloc and then release the object immediately after passing it to the default notification center?

FileItem *item = [[FileItem alloc] init];
[[NSNotificationCenter defaultCenter] postNotificationName:@"dataReceived" object:self userInfo:item];
[item release];

I’m trying to get convention here as I assume that whenever I pass an object as parameter in a message to another object, the receiving object would do a retain if it needs to, and that I can safely release the said parameter?

Answer 1

The second option is the correct one. You could also just do the following:

FileItem *item = [[[FileItem alloc] init] autorelease];
[[NSNotificationCenter defaultCenter] postNotificationName:@"dataReceived" object:self userInfo:item];

The conventional wisdom is that for every alloc, copy, or retain, you need a corresponding release (or autorelease). Doing anything more is almost guaranteed to result in your object being overreleased.