forwarding a notification to another class

Question

I am using this method

- (void)keyboardWillShow:(NSNotification *)notification

that is triggered when the keyboard shows.

When this method is triggered, it receives a notification that contains several parameters about the keyboard, as the animation duration, animation curve and frame. I need to forward this notification and all its parameters to another class. So, I've tried to do this inside keyboardWillShow:

[[NSNotificationCenter defaultCenter] 
 postNotificationName:@"doSomething" object:notification userInfo:nil];

the doSomething notification runs doSomething method on another class, and it has this form:

- (void) doSomething:(NSNotification *)notification {

but when I try to read the notification values on this other class, using, for example,

myRect = [[[notification userInfo] objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];

I obtain zero for all values. The notification is losing its parameters and not being forwarded. How can I do that?

thanks.

Answer 1

It is losing all the values because you passed nil when you created the new notification! You must pass the keyboard notification's userInfo dictionary if you want this to work. So:

[[NSNotificationCenter defaultCenter] 
 postNotificationName:@"doSomething" object:self userInfo:userInfo];

In this case, the object creating this notification is this object. If you want this to appear as to come from the keyboard object, then send [notification object] for object, but I don't recommend this. Also, why not simply have the class that you want to respond to these notifications ALSO listen for keyboard notifications? Creating and sending a new notification from within the keyboard notification call-back seems kind of round-about to me. The other option is to create a delegate-style thing where the class (I am assuming a view controller or something?) actually listening for keyboard notifications then calls back a delegate object (that other class that you want to forward this info to) and passes the userInfo dictionary to it directly. So:

// Assume a proper delegate is set and it responds to - (void)doSomething:(NSDictionary*)userInfo
[delegate doSomething:userInfo]; // from within the keyboard notification

Still, I think I would just have this other class listen for keyboard notifications itself, though.