Sharing data between an IOS Utility Application views - ios

Question

I have created a very basic application using the Utility Application template in Xcode 4.2 in which I want an integer variable obtained from a slider or text field in my FlipsideViewController available in my MainViewController.
I have been searching for hour on global variables but can't find a nice simple answer that works for my specific case.
Please help
(note: I am very new at developing for IOS and objective C. Dumb your answer down for me as much as you are capable!)
Thanks a lot
The following is a basic version of my code showing what I want to do.
FlipSideViewController.h
#import <UIKit/UIKit.h>
#class FlipsideViewController;
#protocol FlipsideViewControllerDelegate
- (void)flipsideViewControllerDidFinish:(FlipsideViewController *)controller;
#end
#interface FlipsideViewController : UIViewController
#property (weak, nonatomic) id <FlipsideViewControllerDelegate> delegate;
- (IBAction)done:(id)sender;
- (IBAction)sliderChange:(id)sender;
#property (weak, nonatomic) IBOutlet UILabel *sliderValueOnFlipside;
#end
FlipSideViewController.m
#import "FlipsideViewController.h"
#interface FlipsideViewController ()
#end
#implementation FlipsideViewController
#synthesize sliderValueOnFlipside;
- (void)viewDidLoad
{
[super viewDidLoad];
}
- (void)viewDidUnload
{
[self setSliderValueOnFlipside:nil];
[super viewDidUnload];
}
- (BOOL)shouldAutorotateToInterfaceOrientation: (UIInterfaceOrientation)interfaceOrientation
{
return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}
#pragma mark - Actions
- (IBAction)done:(id)sender
{
[self.delegate flipsideViewControllerDidFinish:self];
}
- (IBAction)sliderChange:(id)sender {
UISlider *slider = (UISlider *) sender;
int var = [slider value];
sliderValueOnFlipside.text = [NSString stringWithFormat:#"Slider Value is %d",var];
}
#end
MainViewController.h
#import "FlipsideViewController.h"
#interface MainViewController : UIViewController <FlipsideViewControllerDelegate>
- (IBAction)showInfo:(id)sender;
#property (weak, nonatomic) IBOutlet UILabel *sliderValueOnMain;
#end
MainViewController.m
#import "MainViewController.h"
#interface MainViewController ()
#end
#implementation MainViewController
#synthesize sliderValueOnMain;
- (void)viewDidLoad
{
[super viewDidLoad];
sliderValueOnMain.text = [NSString stringWithFormat:#"Slider Value from flipside is %d", var];
}
- (void)viewDidUnload
{
[self setSliderValueOnMain:nil];
[super viewDidUnload];
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}
#pragma mark - Flipside View
- (void)flipsideViewControllerDidFinish:(FlipsideViewController *)controller
{
[self dismissModalViewControllerAnimated:YES];
}
- (IBAction)showInfo:(id)sender
{
FlipsideViewController *controller = [[FlipsideViewController alloc] initWithNibName:#"FlipsideViewController" bundle:nil];
controller.delegate = self;
controller.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
[self presentModalViewController:controller animated:YES];
}
#end
I can easily get the value of the slider to be displayed on the flipside view however I also want that value displayed on the main view.

Answer 1

Global variables are generally frowned upon in polite programming circles.
If you want a method in MainViewController to react to a change in state in FlipsideViewController, then you could make MVC a delegate of FVC, and have FVC call a method on MVC when the value changes.
There's a good explanation of the delegate design pattern here: http://mobiledevelopertips.com/objective-c/the-basics-of-protocols-and-delegates.html