How do I access variable values from one view controller in another?

Question

I have an integer variable (time) in one view controller whose value I need in another view controller. Here's the code:

MediaMeterViewController

// TRP - On Touch Down event, start the timer
-(IBAction) startTimer
{
    time = 0;
    // TRP - Start a timer
    timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(updateTimer) userInfo:nil repeats:YES];

    [timer retain];     // TRP - Retain timer so it is not accidentally deallocated

}

// TRP - Method to update the timer display
-(void)updateTimer
{
    time++;
//  NSLog(@"Seconds: %i ", time); 
    if (NUM_SECONDS == time)
        [timer invalidate];
}

// TRP - On Touch Up Inside event, stop the timer, decide stress level, display results
-(IBAction) btn_MediaMeterResults
{
    [timer invalidate];
    NSLog(@"Seconds: %i ", time);
    ResultsViewController *resultsView = [[ResultsViewController alloc] initWithNibName:@"ResultsViewController" bundle:nil];
    [self.view addSubview:resultsView.view];
}

And in ResultsViewController, I want to process time based on its value

ResultsViewController

- (void)viewDidLoad 
{
    if(time < 3)
       {// Do something}

    else if ((time > 3) && (time < 6))
       {// Do something else}

//etc...

    [super viewDidLoad];
}

I'm kind of unclear on when @property and @synthesize is necessary. Is that the case in this situation? Any help would be greatly appreciated.

Thanks! Thomas

2 revs · Accepted Answer · 2010-03-31 00:36:20Z

6

Declare time as a property in MediaMeterViewController:

@property (nonatomic) NSInteger time;

Whenever you need to access an instance variable in another object, you should have the instance variable declared as a property, and when you declare a property you must always use @synthesize (to synthesize the getter and setter for that property).

Also take note that when setting time in MediaMeterViewController you must always use self.time instead of time. For example, time = 0; should be self.time = 0;.

To access time from your ResultsViewController, you would do something like this:

- (void)viewDidLoad 
{
    [super viewDidLoad];
    if (mmvc.time < 3)
    {
        // Do something
     }

    else if ((mmvc.time > 3) && (mmvc.time < 6))
    {
    // Do something else
    }

    // etc...    
}

Where mmvc is a reference to your MediaMeterViewController object. Hope this helps.

edited Mar 31, 2010 at 0:36

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2 revs
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2 Comments

Thomas Over a year ago

Thanks very much for the answer! I had a few issues getting it to compile, but I didn't realize that in addition to #import "MediaMeterViewController.h" I had to also have @class MediaMeterViewController.

Malloc Over a year ago

Hi, i have question related to that, if i have a NSString at the place of NSInteger(time), am i obliged to do @property (nonatomic,retain) NSInteger time; ? or without retain ?? thx

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