检测AVPlayer和AVQueuePlayer KVO之间的差异

Question

I have a AVPlayer for online audio stream & AVQueuePlayer for offline queue to play multiple songs.

MyCode

self.myQueuePlayer?.addObserver(self, forKeyPath: "timedMetadata", options: NSKeyValueObservingOptions.new, context: nil)

myPlayer.currentItem?.addObserver(self, forKeyPath: "timedMetadata", options: [.new,.old,.initial], context: nil)

How can I observer KVO for "timedMetadata" & get is it AVPlayer or AVQueuePlayer ?

Answer 1

You can use the context argument to distinguish between different KVO objects:

// class
private var playerContext = 0
private var queuePlayerContext = 0

func setup() {
    self.myQueuePlayer?.addObserver(self, forKeyPath: "timedMetadata", options: .new, context: &queuePlayerContext)
    myPlayer.currentItem?.addObserver(self, forKeyPath: "timedMetadata", options: .new, context: &playerContext)
}

override open func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
    guard let context = context else {
        return
    }

    if keyPath == "timedMetadata" {
        switch context {
        case &queuePlayerContext:
            print("queuePlayer")
        case &playerContext:
            print("playerContext")
        default:
            break
        }
    }
}