ios - Update parent view from child view -

i using xcode 5 (ios sdk 7.0). trying update element inside parent view child view.

i have following files: viewonecontroller viewtwocontroller

inside viewonecontroller, adding viewtwocontroller subview following code:

[self.view addsubview:viewtwocontroller]; 

i have uiimageview declated in viewonecontroller.h

iboutlet uiimageview *box; 

i update backgound color of box viewtwocontroller. know can update background color following code.

[box setbackgroundcolor:[uicolor redcolor]]; 

but works in viewonecontroller. have function called updatecolor viewtwocontroller. want update color of box function.

one quick , not clean way call parentviewcontroller directly :

[((viewonecontroller*)self.parentviewcontroller).box setbackgroundcolor:[uicolor redcolor]]; 

however larme suggested it, believe cleanest way use delegate, used notify change after user did something. here tutorial http://www.tutorialspoint.com/ios/ios_delegates.htm

you have create delegate protocol in viewtwocontroller.h

@protocol viewtwodelegate <nsobject>     - (void)somethinghappenedinviewtwocontroller; @end  @interface viewtwocontroller : uiviewcontroller  .... @property (nonatomic,weak) id<viewtwodelegate> delegate; 

in viewonecontroller have set controller delegate viewtwocontroller. in viewonecontroller.h first declare controller implement viewtwodelegate protocol

@interface viewonecontroller:uiviewcontroller<viewtwodelegate> 

and in viewonecontroller.m when create viewtwocontroller :

viewtwocontroller = [[viewtwocontroller alloc] init]; viewtwocontroller.delegate = self; 

and add following method below

- (void)somethinghappenedinviewtwocontroller{     [box setbackgroundcolor:[uicolor redcolor]]; } 

then in viewtwocontroller.m call method, call method implemented in viewonecontroller

[self.delegate somethinghappenedinviewtwocontroller];