1 2014-06-11 15:19:17.167 ***[930:707] *** Terminating app due to uncaught exception ‘CALayerInvalidGeometry‘, reason: ‘CALayer position contains NaN: [160 nan]‘ 2 *** Call stack at first throw: 3 ( 4 0 CoreFoundation 0x3365d64f __exceptionPreprocess + 114 5 1 libobjc.A.dylib 0x33aa0c5d objc_exception_throw + 24 6 2 CoreFoundation 0x3365d491 +[NSException raise:format:arguments:] + 68 7 3 CoreFoundation 0x3365d4cb +[NSException raise:format:] + 34 8 4 QuartzCore 0x361db61d _ZL18CALayerSetPositionP7CALayerRKN2CA4Vec2IdEEb + 140 9 5 QuartzCore 0x361db58b -[CALayer setPosition:] + 38 10 6 QuartzCore 0x361db4d7 -[CALayer setFrame:] + 390 11 7 UIKit 0x330eb455 -[UIView(Geometry) setFrame:] + 188 12 8 UIKit 0x3314854f -[UITableViewCell setFrame:] + 98 13 9 UIKit 0x33147b3b -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:withIndexPath:] + 850 14 10 UIKit 0x3314776b -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:] + 34 15 11 UIKit 0x331400cd -[UITableView(_UITableViewPrivate) _updateVisibleCellsNow:] + 936 16 12 UIKit 0x3313f27d -[UITableView layoutSubviews] + 140 17 13 UIKit 0x330eb5fb -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 26 18 14 CoreFoundation 0x335caf03 -[NSObject(NSObject) performSelector:withObject:] + 22 19 15 QuartzCore 0x361dcbb5 -[CALayer layoutSublayers] + 120 20 16 QuartzCore 0x361dc96d CALayerLayoutIfNeeded + 184 21 17 QuartzCore 0x361e21c5 _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 212 22 18 QuartzCore 0x361e1fd7 _ZN2CA11Transaction6commitEv + 190 23 19 QuartzCore 0x361db055 _ZN2CA11Transaction17observer_callbackEP19__CFRunLoopObservermPv + 56 24 20 CoreFoundation 0x33634a35 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 16 25 21 CoreFoundation 0x33636465 __CFRunLoopDoObservers + 412 26 22 CoreFoundation 0x3363775b __CFRunLoopRun + 854 27 23 CoreFoundation 0x335c7ec3 CFRunLoopRunSpecific + 230 28 24 CoreFoundation 0x335c7dcb CFRunLoopRunInMode + 58 29 25 GraphicsServices 0x3413041f GSEventRunModal + 114 30 26 GraphicsServices 0x341304cb GSEventRun + 62 31 27 UIKit 0x33114d69 -[UIApplication _run] + 404 32 28 UIKit 0x33112807 UIApplicationMain + 670 33 29 PXiPhone 0x000028df main + 70 34 30 PXiPhone 0x00002894 start + 40 35 ) 36 terminate called after throwing an instance of ‘NSException
今天，加完一个功能，在iPhone4上报以上异常，然后crash掉，iPhone3上没事。百思不得其解，于是google之。看了一篇*.com 的文章，说是某些地方代码除以0了，多见于自定义的UITableView自定义UITableViewCell高度的地方，如：tableView:heightForHeaderInSection:或tableView:heightForFooterInSection:。这两个delegate方法都没有地方需要除的。在仔细看一下文章，说多见于适用sizeWithFont方法计算UILabel宽高的地方。恍然大悟，小弟有一个地方使用了UILabel来显示文本，需要用到sizeWithFont方法计算宽高的，在NSString为nil的时候，sizeWithFont会除以0了。
PS:在使用sizeWithFont计算UItabelView中label中字的长度时，由于表视图的cell是复用的，所以在计算label中的NSString的长度时，NSString可能为nil，此时可能会除以0，便会报错。
原文：http://www.cnblogs.com/yuanyuandachao/p/3851745.html