Question

i’m a little bit confused with memory management in view controllers.

Lets say i have header file like this:

@interface MyController : UIViewController {
    NSMutableArray  *data;
}
@property (nonatomic, retain) NSMutableArray *data;
@end

and .m file looks like that:

@implementation MyController
@synthesize data;

- (void)dealloc
{
    [self.data release];
    [super dealloc];
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    if (self.data == nil)
        self.data = [[NSMutableArray alloc] init];
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    [self.data release];
    self.data = nil;
}

Is that ok from the correct memory management point of view? Will that work after dealloc via Memory Warning? How You do that in your apps?

Thanks for your answers 😉

Answer 1

While the alloc-retain calls balance out in viewDidLoad and viewDidUnload and should prove no problem memory-wise, it would be cleaner to take ownership only once and relinquishing it once rather than twice.

- (void)viewDidLoad
{
    [super viewDidLoad];

    if (self.data == nil)
        self.data = [NSMutableArray array];
}

and

- (void)viewDidUnload
{
    [super viewDidUnload];

    self.data = nil;
}