Question

I have a int that resets itself every time the view re-opens/leaves. I have tried every way of declaring the int that i can think of, from public, to instance variable to global variable, but it still seems to reset!

@interface MainGameDisplay : UIViewController
extern int theDay;

@implementation MainGameDisplay

- (void)viewDidLoad {
    [super viewDidLoad];
    NSLog(@"%i", theDay);
}

- (IBAction)returnToHome:(id)sender {
        ViewController *new = [[ViewController alloc] initWithNibName:nil bundle:nil];
        [self presentViewController: new animated:YES completion:NULL];
        NSLog(@"%i", theDay);
}

- (IBAction)theDayAdder:(id)sender {
    theDay++;
}

Okay so theDay is a global integer variable. on View load NSLog returns an output of 0. I can then click theDayAdder as many times as I want, and when I click returnToHome, it will tell me what theDay is. When I come back to MainGameDisplay page however, theDay will be reset back to zero, even though it is a global variable?

Output:
0
N (number of times you clicked 'theDayAdder' button)
0

Answer 1

The problem is that you alloc init’ing a new instance of MainGameDisplay every time you go back to it, so of course your global variable will be reset to 0. You need to create a property (typed strong) in ViewController, use that to go back to the same instance each time.

- (IBAction)returnToGameDisplay:(id)sender {
     if (! self.mgd) {
        self.mgd = [[MainGameDisplay alloc] initWithNibName:nil bundle:nil];
     }
     [self presentViewController: self.mgd animated:YES completion:NULL];
     NSLog(@"%i", theDay);
}

In this example mgd is the property name created in the .h file.