iphone - iOS: keeping property values while switching between UITabBarItem's -

i have uitabbarcontroller linked 2 uiviewcontrollers, , in "first" uiviewcontroller have properties values need maintained when switch other view controller , back. instead, value of properties reset every time switch view controllers. how fix that? thanks!

edit:

heres code in uiviewcontroller (the scrollview under tab bar , navigation bar have on top):

splitbillviewcontroller.m

@interface splitbillviewcontroller ()  @property (nonatomic) nsmutablearray *defpricesarray; @property (nonatomic) nsmutablearray *defqtyarray; @property (nonatomic) nsmutablearray *deftickarray; @property (nonatomic) nsmutablearray *defpeoplearray; @end  @implementation splitbillviewcontroller   - (void)viewdidload{     [super viewdidload]; }  -(nsmutablearray *)defpeoplearray{     if(!_defpeoplearray){         _defpeoplearray=[[nsmutablearray alloc] initwithobjects:@"1", nil];     }     return _defpeoplearray; } -(nsmutablearray *)defqtyarray{     if(!_defqtyarray){         _defqtyarray=[[nsmutablearray alloc] initwithobjects:@"1", nil];     }     return _defqtyarray; } -(nsmutablearray *)defpricesarray{     if(!_defpricesarray){         _defpricesarray=[[nsmutablearray alloc] initwithobjects:@"0.00", nil];     }     return _defpricesarray; } -(nsmutablearray *)deftickarray{     if(!_deftickarray){         _deftickarray = [[nsmutablearray alloc] initwithobjects:[nsnumber numberwithint:1], nil];     }     return _deftickarray; }     -(void)viewwillappear:(bool)animated{     n=1;     aid=@"";    uitapgesturerecognizer *tap = [[uitapgesturerecognizer alloc]                                    initwithtarget:self                                    action:@selector(dismisstippercentage)];      [self.view addgesturerecognizer:tap];     if (iphone5){         self.view.backgroundcolor=[uicolor colorwithpatternimage:[uiimage imagenamed:@"background-568h"]];     }     else {         self.view.backgroundcolor = [uicolor blackcolor];     }     [self.scrollview addsubview:self.itemtable];     [self.scrollview addsubview:self.totalvalue];     [self.scrollview addsubview:self.tip];     [self.scrollview addsubview:self.tippercentage];     [self.scrollview addsubview:self.addedvalue];     [self.scrollview addsubview:self.perperson];     self.scrollview.alpha=1;     if (!iphone5)[self.scrollview setbackgroundcolor:[uicolor colorwithpatternimage:[uiimage imagenamed:@"scrollviewbackground"]]];     else [self.scrollview setbackgroundcolor:[uicolor colorwithpatternimage:[uiimage imagenamed:@"scrollviewbackground-568h"]]]; }