如    [__NSArrayM insertObject:atIndex:]: 這種只會顯示在main 怎麼找出問題點   http://stackoverflow.com/questions/13929518/nsarraym-insertobjectatindex-object-cannot-be-nil-how-determine-where-i    1) goTo the breakpoint tab in Xcode.   2) click on the '+" button at the bottom.   3) Add Exception Breakpoint   a) In the break tab select both:    i )  on Throw      ii )  on Catch    and build and r un.    4) These breakpoints will give you exactly where your app is crashing 90% of the times.