objective c - push and pop information from DetailViewController to MasterViewController -

i'm making small ipad app using splitviewcontroller , working masterviewcontroller on detailviewcontroller. trying push data detailviewcontroller masterviewcontroller. once information pushed masterviewcontroller want make use of im using pop method.

the push method populates array- reason array recreated every time call pushmoduletitle method , hold 1 object @ time.

in detailviewcontroller.m

- (ibaction)buttonaddpressed:(id)sender {     cw3masterviewcontroller *master = [[cw3masterviewcontroller alloc]init];     [moduletitles addobject:textfieldmoduletitle.text];     [master pushmoduletitle:self.textfieldmoduletitle.text];); } 

in masterviewcontroller.m

 - (nsmutablearray *)moduletitlestack//init array     {         if (!_moduletitlestack){             _moduletitlestack = [[nsmutablearray alloc] init];         }         return _moduletitlestack;     }      -(void)pushmoduletitle:(nsstring*)moduletitile     {         nsstring * moduletitileobject = moduletitile;         [self.moduletitlestack addobject:moduletitileobject];         nslog(@"%@",self.moduletitlestack);      } 

so use information pushed i'm using pop method: - alway returns me null value , when put break point indicates moduletitlestack has 0 objects. i'm not sure why.

-(nsstring *)popmoduletitle {     nsstring * moduletitileobject = [self.moduletitlestack lastobject];     if (moduletitileobject)[self.moduletitlestack removelastobject];     return moduletitileobject; } 

calling popmoduletitle method: gives null value

- (ibaction)testbuttonpressed:(id)sender {      nslog(@"%@", [self popmoduletitle]);  } 

the reason same answer other question asked. creating new instance of cw3masterviewcontroller every time click button. should reference master controller this:

cw3masterviewcontroller *master = self.splitviewcontroller.viewcontrollers[0]; 

this assumes master controller @ index 0 of split view controller. if it's embedded in navigation controller (which is), need go little further master:

cw3masterviewcontroller *master = (cw3masterviewcontroller *)[(uinavigationcontroller *) self.splitviewcontroller.viewcontrollers[0] topviewcontroller];