What causes this error? “CALayer position contains NaN: [240 nan]”

Question

I\'ve seen this happen whenever i rotate a screen that has a UITableView on it. I\'ve found out that it happens inbetween the willRotate and

Answer 1

(Decided to take this out of comments and put it as an answer, since I think it's a darned good answer :)

Ha! I had an NaN calculation (div0), too. Key debugging aid: the message in question is output by NSLog(), so set a breakpoint on NSLog() and watch what the OS is doing at that time. For me, it was myUISlider.value = NaN.

To set breakpoint:

XCode 3.x

• CMD-SHIFT-Y (debug window.)
• Breakpoints button.
• "Double-click for symbol"
• Type in "NSLog" (no quotes.)

XCode 4.x

• CMD-6 (breakpoints navigator.)
• "+" to add breakpoint (lower left.)
• Select ADD SYMBOLIC BREAKPOINT.
• Symbol: NSLog
• Confirm: Done.

XCode 5.x - 7.1 (at least) (Same as 4.x, except breakpoints navigator is CMD-7, now.)

Run app, watch it break on NSLog, check the stack traces.