Slow response using NSNotification defaultCenter - ios

Question

Hi I am using NSNotificationCenter defaultCenter to implement the 'like' and 'comment' functions in my app.
//In Answer Table View
#implementation AnswerTableView
- (id)initWithParentController:(UIViewController *)pController andResourcePath:(NSString *)thisResourcePath {
....
// Notification to reload table when a comment is submitted
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(reloadTable)
name:#"Comment Submitted"
object:nil];
// Notification to reload table when an answer is liked
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(reloadTable)
name:#"Answer Liked"
object:nil];
}
- (void)dealloc {
[[NSNotificationCenter defaultCenter] removeObserver:self];
[super dealloc];
}
//In custom button implementation - THIS BUTTON IS CREATED IN EVERY CELL OF THE TABLEVIEW
#implementation UICustomButton
-(id)initWithButtonType:(NSString *)type {
self = [super init];
if (self) {
//Initialization done here
}
return self;
}
- (void)buttonPressed {
if ([btnType isEqualToString:#"like"]) {
[[NSNotificationCenter defaultCenter] postNotificationName:#"Answer Liked" object:nil];
}
else if ([btnType isEqualToString:#"comment"]) {
[[NSNotificationCenter defaultCenter] postNotificationName:#"Comment Submitted" object:nil];
}
}
However, I realize that after using these functions for a while, the response speed of the table reload gets slower and slower (to a point where it crashes).
Did I miss out anything in the implementation i.e. deallocating etc

Answer 1

You are repeatedly adding observers and the slowdown occurs because the notification code has to cycle over more and more observers to send notifications. You are probably crashing because you are leaking so many of these views.
Put a log statement in your dealloc to see if these instances are ever cleaned up. Also there can be timing issues with removeObserver in a dealloc method. try to remove the observer before dealloc if you can.

Answer 2

Sometimes its good to queue the event with Grand Central Dispatch to make sure its running on the main thread.
dispatch_async(dispatch_get_main_queue()