ios - UIApplication sharedApplication EXC BAD ACCESS in a UITextField category -

- (void)somemethod { bool isrighttoleft = ([uiapplication sharedapplication].userinterfacelayoutdirection == uiuserinterfacelayoutdirectionrighttoleft) } 

this causes exc bad access. i'm thinking because not thread safe , called many times. rules in using uiapplication sharedapplication? thanks!