How to send a string along with NSNotification? - objective-c

Question

I'm trying to write a plugin for phonegap/cordova that allows audio to resume when interrupted by a phone call. I'm using AVAudioSesionInterruptionNotification and it is working well. However, I need to be able to send a string to my event handler, but I can't figure out how.
I'm setting up an event listener here and calling it from the javascript layer:
- (void) startListeningForAudioSessionEvent:(CDVInvokedUrlCommand*)command{
NSString* myImportantString = [command.arguments objectAtIndex:0];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(onAudioSessionEvent:) name:AVAudioSessionInterruptionNotification object:nil];
}
and I'm handling the event here:
- (void) onAudioSessionEvent:(NSNotification *)notification
{
if([[notification.userInfo valueForKey:AVAudioSessionInterruptionTypeKey] isEqualToNumber:[NSNumber numberWithInt:AVAudioSessionInterruptionTypeEnded]]){
//do stuff using myImportantString
}
}
can't figure out how to pass myImportantString over to onAudioSessionEvent. I know very little Objective-C (hence my use of cordova), so please respond as if you're talking to a child. Thanks!
By the way, I'm simply trying to add a couple of methods on top of cordova's media plugin found here: https://github.com/apache/cordova-plugin-media/tree/master/src/ios
so the code above is the entirety of my .m file minus this part
#implementation CDVSound (extendedCDVSound)

Answer 1

It's probably easier to use the block-based API for adding an observer:
- (void) startListeningForAudioSessionEvent:(CDVInvokedUrlCommand*)command{
NSString* myImportantString = [command.arguments objectAtIndex:0];
id observer = [[NSNotificationCenter defaultCenter] addObserverForName:AVAudioSessionInterruptionNotification
object:nil
queue:nil
usingBlock:^(NSNotification *notification){
if([[notification.userInfo valueForKey:AVAudioSessionInterruptionTypeKey] isEqualToNumber:[NSNumber numberWithInt:AVAudioSessionInterruptionTypeEnded]]){
//do stuff using myImportantString; you could even skip the use of that
//temporary variable and directly use [command.arguments objectAtIndex:0],
//assuming that command and command.arguments are immutable so that you
//can rely on them still being the same
}
}];
}
By using the block-based API, you can directly reference any variables that are in scope at the time the observer is added in the code which is invoked when the notification is posted.
When you're done observing, you need to remove observer as an observer of the notification.

Answer 2

Like this:
// near the top of MyController.m (above #implementation)
#interface MyController ()
#property NSString *myImportantString;
#end
// inside the implementation
- (void) startListeningForAudioSessionEvent:(CDVInvokedUrlCommand*)command{
self.myImportantString = [command.arguments objectAtIndex:0];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(onAudioSessionEvent:) name:AVAudioSessionInterruptionNotification object:nil];
}
- (void) onAudioSessionEvent:(NSNotification *)notification
{
if([[notification.userInfo valueForKey:AVAudioSessionInterruptionTypeKey] isEqualToNumber:[NSNumber numberWithInt:AVAudioSessionInterruptionTypeEnded]]){
//do stuff using self.myImportantString
}
}