/*

    File:       QWatchedOperationQueue.h

    Contains:   An NSOperationQueue subclass that calls you back when operations finish.

    Written by: DTS

    Copyright:  Copyright (c) 2011-2013 Apple Inc. All Rights Reserved.

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*/

#import <Foundation/Foundation.h>

@interface QWatchedOperationQueue : NSOperationQueue

{

    id                      _target;

    NSThread *              _targetThread;

    CFMutableDictionaryRef  _operationToAction;

}

- (id)initWithTarget:(id)target;

    // Initialise the object to call selectors on target on the current thread.

    // target is /not/ retained, so we expect target's -dealloc method to call 

    // -invalidate.

@property (atomic, assign, readonly) id             target;

    // The target object established when the object was initialised.

@property (atomic, strong, readonly ) NSThread *    targetThread;

    // The target thread established when the object was initialised.

- (void)addOperation:(NSOperation *)operation finishedAction:(SEL)action;

    // Add an operation to the queue, calling the action on the target on 

    // the target thread once it has finished.

    //

    // IMPORTANT: The action is /not/ called if the operation is cancelled. 

    // This cancellation check is done on the target thread just before the 

    // action is called, so to avoid race conditions, it's best to cancel 

    // your operations from the target thread.

    //

    // This may be called on any thread.

- (void)invalidate;

    // Invalidate the queue, preventing any further calls to target.

    //

    // This must be called on the target thread.

@end