How to get a list of NSNotifications?

kevgski

I’ve been pretty interested in property observers lately and eventually want to write a little blog post about what I have discovered however I am stumbling getting a list of all the notifications being used in the app.

I found this bit of swift code from here: https://nshipster.com/nsnotification-and-nsnotificationcenter/

let center = NSNotificationCenter.defaultCenter()
center.addObserverForName(nil, object: nil, queue: nil) { notification in
    print("\(notification.name): \(notification.userInfo ?? [:])")
}

Unfortunately, I think it is a closure and I’m not sure how that translates to Javascript. Any ideas?

mathieudutour

blocks have always been a pain in cocoascript yes.

You can try something like:

let center = NSNotificationCenter.defaultCenter()
center.addObserverForName_object_queue_usingBlock(null, null, null, __mocha__.createBlock_function('v16@?0@"NSNotification"8', function (notification) {
  console.log(notification.name())
})

(see https://sketchplugins.com/d/796-distributing-and-updating-sketch-libraries/59)

You will need a fiber to keep your script around until you receive a notification

kevgski

Sweet! This worked great. Though Sketch slowed down to a halt trying to log all those notifications 😂😅 I guess that is to be expected.

Tons of great notification events. Any idea how to filter the notifications to just Sketch created ones? All the NS ones are pretty helpful but events like mirror-did-update-document and MSDocumentDidBecomeCurrentNotification are interesting.

mathieudutour

The first argument of addObserverForName_object_queue_usingBlock is the notification name, so if you put mirror-did-update-document, then you will only receive those ones.

If you want to filter out the ones that starts with NS, you can do something like if (!String(notification.name()).startsWith('NS)) { console.log(notification.name()) }.

But do keep in mind that those notification names are private APIs, just like the rest of the obj-c API 🙂

kevgski

Cool! Definitely understand the usage of those private APIs. Just wanted to tinker with what all was getting logged. I’m mostly interested in the generic NS notifications but its fun to see all what is being used by Sketch too.

By the way, is this notification structure how the Action API works? Does the Action API interact with NSNotificationCenter at all?

kevgski

The main reason why I’m looking into this sort of thing is because I was needing a way to get substring selection updates for my typography tool (https://github.com/BohemianCoding/SketchAPI/issues/454). I’m able to trigger a function from NSTextViewDidChangeSelectionNotification

kevgski

Hmm I've tried getting this work again but it doesn't seem to behave as expected anymore.

Just getting a bunch of unrecognized selector sent to instance...

default	17:20:39.271423-0800	Sketch Beta	-[__NSFrozenDictionaryM callJSFunction:withArgumentsInArray:]: unrecognized selector sent to instance 0x60000125eca0