UIScrollView _getDelegateZoomView bug 經歷

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[UIScrollView _getDelegateZoomView]
UIKit -[UIScrollView_offsetForCenterOfPossibleZoomView:withIncomingBoundsSize:] + 64

bugly 騰訊給出的解釋

閃退場景一：recorder deleteRecording 之前 先判斷文件是否存在，否則會造成過度釋放，解決方法:

if ([[NSFileManager defaultManager] fileExistsAtPath:self.recorder.url.path]) {
if ([self.recorder deleteRecording])
NSLog(@"Failed to delete %@", self.recorder.url);
}

閃退場景二： delegate = nil 。
將XXViewContrller設置爲delegate時，當頁面發生跳轉時，XXViewController的對象會被釋放，這是代碼走到[_delegate callbackMethod],便出現crash。解決方法有二：1.將@property (nonatomic ,assign) id

http://www.cnblogs.com/smileEvday/p/iOSCrash.html

• http://artsy.github.io/blog/2015/07/30/Notorious-BUG-Part-1/

Perfect, an exact replica of the crash report, so now I know with confidence that the problem is that theARArtworkViewControlleris released by the time that method is called.

問題的方向是對的，都是vc提前釋放，然後野指針的問題引起，
block 強引用同樣會產生此類問題