Prepares a music player for playback.
- iOS 10.1+
- Media Player
A block that is called after the first item in the queue is buffered and ready to play.
If an error occurred, this parameter holds the error object that explains the error. Otherwise, the value of this parameter is
Call this function to ensure that the first item in the queue has been buffered and is ready to play. Code inside the completion handler is executed after the first item in the queue has been buffered.