What is the significance of WaitUntilDOne in performSelectorOnMainThread?
WaitUntilDOne
performSelectorOnMainThread
IN what way the YES or NO set to Wait
YES
NO
Wait
YES means the current thread blocks / waits until the selector is performed, NO to have performSelectorOnMainThread:withObject:waitUntilDone: returns immediately
performSelectorOnMainThread:withObject:waitUntilDone: