Question

I have accounts which they have some settings attributes. As settings there are value of UISlider and value of UISwitch. When i run the application it works fine i can display the last value from NSUserDefaults because viewDidLoad method works. My application has a tab bar controller by the way. So when i switch tabs it works fine too because i can get the values of switch and slider and update them in viewWillAppear method. But in my setting switch, i present a view which there are user list in it, so the user can select any account. When i get back from presented view i can’t update the values of switch and slider. I need a trigger method to update their values. Is there any way to do that?

Answer 1

Yes this are the 3 apple ways to do it:

1) Delegation
2) NSNotificationCenter
3) KVO

However for your particular case a modal view, the delegation pattern is the one Apple recommends, and is the one I would recommend as well.

It requires a bit more coding than the other 2 options though.

First you have to declare the protocol in the view you are presenting modally:

in your .h

@protocol MyProtocol;

@interface MyClass : NSObject

@property (nonatomic, weak) id<MyProtocol> delegate;

@end

@protocol MyProtocol <NSObject>

-(void)updateValues:(NSArray *)values;

@end

Then before presenting the modal view modally from the original view controller simply set the delgate like this

myModallyPresentedController.delegate = self;

Then have your presenting view controller adopt the protocol

in your .h

MyPresentingViewController : UIViewController <MyProtocol>

in .m

//Implement method:

-(void)updateValues:(NSArray *)values {
   //Update Values.
}

Finally when user presses “Done”

you can call

[delegate updatedValues:myValues];

And update accordingly.

Hope that helps.