Some tricks may have you save days

For iOS, I sometimes met wried issues and have no solution for that at all, seems simple things and sometimes can be confused, and took you days... not worth at all.

So, hope my tricks can save you days, and welcome sharing, too.

1, To know when the back button of UINativationViewController is clicked, you can try:
(According to here: http://stackoverflow.com/questions/1214965/setting-action-for-back-button-in-navigation-controller/3445994#3445994)

-(void) viewWillDisappear:(BOOL)animated {
    if ([self.navigationController.viewControllers indexOfObject:self]==NSNotFound) {
       // back button was pressed.  We know this is true because self is no longer
       // in the navigation stack.  
    }
    [super viewWillDisappear:animated];
}

2, Skip previous view and go back to previous's previous view, you can try

(e.g. You're at A, and A->B->C, but when back in C, you want to skip B and go to A directly)

a, First, saving current UINavigationViewController to a temporary variable

b, Call popViewControllerAnimated (when you pop, the navigation changed to nil immediately, that's why when you push C doesn't work. You need to save it to a local variable first, retain the couting)

c, Using the one you saved just now to push to show next view C

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