maintain object state when moved away of the screen - ios

Question

I have a class declaration which contains an singleton object that manages the data (called sharedDatacontroller).
Now there are many other screen and declaration is the last one. I have to check if the user moves back from declaration screen and alters any data , then have to reset a switch button on the declaration screen.
My Approach:
-(void) viewWillDisappear:(BOOL)animated
{
self.sharedControllerClone=sharedController;
}
-(void) viewWillAppear:(BOOL)animated
{
if ([self.sharedControllerClone isEqual:sharedController])
{
NSLog(#"Not Same");
self.acceptDeclarationSwitch.on= self.acceptDeclarationSwitch.on;
}
else
{
self.acceptDeclarationSwitch.on= !self.acceptDeclarationSwitch.on;
}
}
But when the control comes in after navigating from back screen , the self.sharedControllerClone is reseting to Nil. How to preserve its state..any ideas?
Hope I am clear this time.

Answer 1

You can try this thing by creating Macros in your AppDelegate and assigning different states to a property taken in AppDelegate so that you will come to know that what is your current state. You can create an object of your AppDelegate in your required controllers and in their ViewDidLoad, you can assign the current state to AppDelegate like this:
//in AppDelegate
#import <UIKit/UIKit.h>
#define FIRST_CONTROLLER 1
#define SECOND_CONTROLLER 2
#define THIRD_CONTROLLER 3
#interface AppDelegate : UIResponder <UIApplicationDelegate>
#property (strong, nonatomic) UIWindow *window;
#property int previousControllerState;
#end
And then, you can set your previousControllerState in the ViewDidLoad of your required controller.
//in your ViewControllers
- (void)viewDidLoad
{
[super viewDidLoad];
app.previousControllerState = FIRST_CONTROLLER;
}
And you can check your state in if condition in the next controller.
You have to take the states in AppDelegate to prevent the objects from getting nil. Otherwise, as soon as you move from one controller to another, the object of the previous controller might be getting nil.