Question

It’s possible this question is already out there, but I couldn’t find it. My question is essentially this. If I have a repeating NSTimer that executes something that takes longer than the timer interval, will there be some thrashing that will crash the app? Alternatively, does the new time event not start until the task being executed completes?

Answer 1

Since the NSTimer runs on the run loop it was created in, I think it can’t ever re-enter the method it calls. This document on the run loops confirms this (see the “Timer Sources” section:

“Similarly, if a timer fires when the run loop is in the middle of
executing a handler routine, the timer waits until the next time
through the run loop to invoke its handler routine”