Can I receive a callback whenever an NSPasteboard is written to?

Question

I\'ve read Apple\'s Pasteboard Programming Guide, but it doesn\'t answer a particular question I have.

I\'m trying to write a Cocoa application (for OS X, not iOS) t

Answer 1

For those who need some very simplified version in Swift 5, it just works(base on @Devarshi code):

    func WatchPasteboard(copied: @escaping (_ copiedString:String) -> Void) {
        let pasteboard = NSPasteboard.general
        var changeCount = NSPasteboard.general.changeCount
        Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { _ in
            if let copiedString = pasteboard.string(forType: .string) {
                if pasteboard.changeCount != changeCount {        
                    copied(copiedString)                
                    changeCount = pasteboard.changeCount
                }
            }
        }
    }

Usage of how to use is as below:

WatchPasteboard {
    print("copy detected : \($0)")
}

it will print out like below..

watched : pasteboard1
watched : pasteboard2