IOS4上的NSOperationQueue滞后

Question

I wrote some sample code in a separate application, that basically queues up items in an NSMutableArray. I then have a method which loops through that array and creates an NSInvocationOperation, puts it in the NSOperationQueue, releases the operation and so forth. The method then gets called (simply prints out the string that was stored in the array and passed into the operation), does it's job, and sends an NSNotification back to the ViewController. The observer method gets hit, but the operations have a lag on them. For instance, the observer method simply updates a UILabel with how many messages are left in the queue. It eventually does this, but there seems to be a five second lag in between all of the NSOperations completing and the UI updating. To me it seems like the NSOperationQueue is blocking the main thread. Is there anyway to get the UI to respond immediately to the notifications?

One important note is that I have not tested this on the phone yet, just the simulator. I'm not sure if this makes a difference.

Sorry in advance. I'm away from my computer and I don't have the code in front of me. Hopefully I explained it well enough. Also I have read the documentation, just haven't found anything that's really answering this specific question for me.

Answer 1

The delay is typical of UI updates that are performed on threads other than main.

To see your update instantly on the UILabel , be sure to invoke whatever method is updating the label's text as follows:

[self performSelectorOnMainThread:@(myMethodToUpdateLabelWithText:) withObject:text waitUntilDone:NO];

where myMethodToUpdateLabelWithText is a method within your class that sets the label's text value.