Use KVO to observe the operations
property of your queue, then you can tell if your queue has completed by checking for [queue.operations count] == 0
.
Somewhere in the file you're doing the KVO in, declare a context for KVO like this (more info):
static NSString *kQueueOperationsChanged = @"kQueueOperationsChanged";
When you setup your queue, do this:
[self.queue addObserver:self forKeyPath:@"operations" options:0 context:&kQueueOperationsChanged];
Then do this in your observeValueForKeyPath
:
- (void) observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object
change:(NSDictionary *)change context:(void *)context
{
if (object == self.queue && [keyPath isEqualToString:@"operations"] && context == &kQueueOperationsChanged) {
if ([self.queue.operations count] == 0) {
// Do something here when your queue has completed
NSLog(@"queue has completed");
}
}
else {
[super observeValueForKeyPath:keyPath ofObject:object
change:change context:context];
}
}
(This is assuming that your NSOperationQueue
is in a property named queue
)
At some point before your object fully deallocs (or when it stops caring about the queue state), you'll need to unregister from KVO like this:
[self.queue removeObserver:self forKeyPath:@"operations" context:&kQueueOperationsChanged];
Addendum: iOS 4.0 has an NSOperationQueue.operationCount
property, which according to the docs is KVO compliant. This answer will still work in iOS 4.0 however, so it's still useful for backwards compatibility.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…