问题
I'd like to retrieve a list of observers (objects and selectors) for a given notification name. I know there's no official API for that. I also know I could subclass NSNotificationCenter to accomplish this. Sometimes however this is not a viable option because NSNotificationCenter usage is spread all over the code or even binary frameworks.
So I'm looking for an unofficial/private way to do this. (Since it's about debugging only, that's fine.)
回答1:
Finally, Apple added a way to print all notification center observers:
po [NSNotificationCenter defaultCenter]
It prints a comma separated list with Name, Object, Observer, and Options:
<NSNotificationCenter:0x7f997b307500>
Name, Object, Observer, Options
WebPreferencesRemovedNotification, 0x11165b680, 0x116c87ff8, 1400
UIApplicationWillEnterForegroundNotification, 0x11165b680, 0x7f997a838000, 1400
...
回答2:
If you don't want to subclass NSNotificationCenter you can rename original addObserver:selector:name:object method and create your own with such name and add observers in there to some array then call original renamed method.
Take a look at following methods: class_addMethod, class_replaceMethod, class_getMethodImplementation.
Also look at this SO question: Method Swizzling
I am not sure why you want observers but you might find this class useful, which removes observers automatically for you which I think might be what you want. SFObservers
来源：https://stackoverflow.com/questions/13271388/how-to-retrieve-all-nsnotificationcenter-observers