Swift Notification

an overview

NotificaitonCenter

• default = per app
• It’s used in register an observer and the listener
• Two types for listener -
  • Selector
    • Based on the observer that this will be gone once the observer does not exist
  • Block (Call back)
    • Based on the func. No needs to specify the observer.
    • Should be manually removed the returned NSObjectProtocol from the listening list.
    • Can specify the desired operation queue.
• addObserver: listener(queue), Notification.Name(id for notification), object(secondary id, usually the sender)
• post - to the queue that specified in the addObserver in sync mode.
  • Notificaiton.Name
  • userInfo - detailed arguments

NotificaitonQueue

• default = per thread
• Used to async post notifications
• It’s scheduled on the RunLoop, so for OperationQueue, which is based on the Grand Central Dispatch, this won’t work unless perform the enqueue in mainRunLoop.
  • Tried on new runLoop, which can’t work also.
• enqueue
  • Notification - the name, object, userInfo
  • postingStyle
    • now - sync
    • asap - async
    • whenIdle - async, not yet know the exact definition of idleness
  • coalesceMask - combine value; remove the extra calls based on name/object/both.
  • forModes - ?