objective c - __NSStackBlock__ isEqualToString: issue -

i experimenting this code. in 1 of viewcontroller's using next snippet:

- (bool)textview:(uitextview *)textview1 shouldchangetextinrange:(nsrange)range replacementtext:(nsstring *)text {     if([text isequaltostring:@"\n"])     {         [textview resignfirstresponder];         return no;     }     return yes; } 

i found in web dismissing keyboard pressing returnbutton. works when calling viewcontroller. in root klnoteviewcontroller adding notification in handle state changes-method:

- (void) setstate:(klcontrollercardstate)state animated:(bool) animated {     [[nsnotificationcenter defaultcenter] postnotificationname:@"refresh" object:self];      if (animated)     {         [uiview animatewithduration:self.noteviewcontroller.cardanimationduration animations:^{             [self setstate:state animated:no];         }];         return;     }     //full screen state     if (state == klcontrollercardstatefullscreen)     {         [self expandcardtofullsize: animated];         [self setycoordinate: 0];     }     //default state     else if (state == klcontrollercardstatedefault)     {         [self shrinkcardtoscaledsize: animated];         [self setycoordinate: originy];     }     //hidden state - bottom     else if (state == klcontrollercardstatehiddenbottom)     {         //move off screen , far enough down shadow not appear on screen         [self setycoordinate: self.noteviewcontroller.view.frame.size.height + abs(self.noteviewcontroller.cardshadowoffset.height)*3];     }     //hidden state - top     else if (state == klcontrollercardstatehiddentop)     {         [self setycoordinate: 0];     }      //notify delegate of state change (even if state changed self)     klcontrollercardstate laststate = self.state;     //update new state     [self setstate:state];     //notify delegate     if ([self.delegate respondstoselector:@selector(controllercard:didchangetodisplaystate:fromdisplaystate:)]) {         [self.delegate controllercard:self               didchangetodisplaystate:state fromdisplaystate: laststate];     } } 

and add adding observer:

[[nsnotificationcenter defaultcenter] addobserver:self selector:@selector(dismisskeyboard) name:@"refresh" object:nil]; 

in every viewcontrollers -viewdidload. when observer used uitextfield works fine, in viewcontroller when using uitext view have crash log:

[nsstackblock isequaltostring:]: unrecognized selector sent instance 0xbfffd228

i searched in web found 2 links explanation of nsstackblock , not informative me solve problem. can explain can be?