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Alan Lee

Alan Lee's Public Library

  • The Voice-Processing I/O unit extends the Remote I/O unit by adding acoustic echo cancelation for use in a VoIP or voice-chat application. It also provides automatic gain correction, adjustment of voice-processing quality, and muting

  • NSNull is used throughout Foundation and other frameworks to skirt around the limitations of collections like NSArray and NSDictionary not being able to contain nil values. You can think of NSNull as effectively boxing the NULL or nil value so that it can be used in collections:


  • simplicity of the work-queue programming model
  • system is able to manage threads much more efficiently than any single application ever could

  • It is also possible to execute an operation object manually by calling its start method, but doing so does not guarantee that the operation runs concurrently with the rest of your code.
  • In an operation object, you specify the thread priority as a floating-point value in the range 0.0 to 1.0, with 0.0 being the lowest priority and 1.0 being the highest priority. If you do not specify an explicit thread priority, the operation runs with the default thread priority of 0.5.
  • This new priority remains in effect for the duration of your operation’s main method only.

  • If you want to reference any object from outside in the block, remember that you should pass in a weak reference.
  • if you want to do something that is related to the UI in the block, you must do it on the main thread

  • They begin with the name of the AppKit or UIKit object doing the delegating

  • must call the endBackgroundTask:
  • generates a unique token to associate with the corresponding task.

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  • The UIApplication object is the first object to receive the event and make the decision about what needs to be done. A touch event is usually dispatched to the main window object, which in turn dispatches it to the view in which the touch occurred. Other events might take slightly different paths through various app objects.
  • action selector
  • target

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