uinavigationbar - Cancel Navigation Bar action in iOS -

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i'm working on ios application involves users filling out text fields , navigating through views. currently, navigation handled using navigation bar, , through buttons. tried make of fields required: preventing progress through application if fields left blank. worked button based navigation not navigation bar. code follows:

- (void)prepareforsegue:(uistoryboardsegue *)segue sender:(id)sender {     if ([[segue identifier] isequaltostring:@"birthpopbus"]) {         currentpopoversegue = (uistoryboardpopoversegue *)segue;         pvc = [segue destinationviewcontroller];         [pvc setdelegate:self];     }     else if([[segue identifier] isequaltostring:@"secondbuspagesegue"]) {         //this code breaks next page          //check fields, , create error message (code removed readability)...          //if fields not filled in, display alert generated string.         if(!(first && last && email && phone && address && zip && ssn && birthfilled)){             uialertview *message = [[uialertview alloc] initwithtitle:@"required fields missing:"                 message:alertmessagemutable                 delegate:nil                 cancelbuttontitle:@"ok"                 otherbuttontitles:nil];             [message show];          }          //perform segue, should run if required fields filled.         else{                  [self fillbus1dictionary];             nslog(@"application dictionary: %@", self.application);              secbuspage * secondbuspage = segue.destinationviewcontroller;             secondbuspage.application = self.application;         }     } }

the error message show up, after view has changed. user gets secondbuspage, , gets alert saying "you didn't fill out fields x, y, z." confusing them. ideas preventing navigation bar switching views?

thanks in advance!

you can achieve implementing conditional segues 1 in answer in below linked post

conditional segue using storyboard

you cannot cancel segue prepareforsegue. instead of perform segues based on condtions


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