What is the significance of WaitUntilDOne in performSelectorOnMainThread?

Question

What is the significance of WaitUntilDOne in performSelectorOnMainThread?

IN what way the YES or NO set to Wait

Answer 1

Generally, you want to avoid blocking the current thread's execution using YES.

If NO, the message will be added to the main thread's run loop's to do list to be performed when the run loop resumes -- that could be soon and practically immediately/concurrently.