Question

I’m using iOS 4 and I have some memory management problems that I don’t understand. I will try to simplify the code:

- (void)viewDidLoad
{
    NSMutableArray *buttonArray = [[NSMutableArray alloc] init];
    for (int i = 0; i < [othercollection count]; i++)
    {
        // Push objects to button array
    }

    self.buttonSliderView = [[ButtonSliderView alloc] initWithButtons:
        buttonArray];
    [buttonArray release];
    [self.view addSubview:self.buttonSliderView];
    [buttonSliderView release];
}

- (void) viewDidAppear 
{
     if ([buttonSliderView.menuButtons count] > 0)
     {
         // ...
     }
}

In ButtonSliderView.m:

- (id)initWithButtons:(NSMutableArray *)buttonArray
{
    self = [super init];
    if (self)
    {
        menuButtons = buttonArray;
    }
 }

I have an error in the first line of viewDidAppear. menuButtons were released. How can I fix this? Which is the correct solution?

If I change button array declaration to this:

NSMutableArray* buttonArray = [[[NSMutableArray alloc] init] autorelease];

…and remove the release sentence, it crashes too. If I remove the release sentence and don’t autorelease, it works, but there are memory leaks.

Answer 1

The problem is that you omit the setter and assign menuButtons property directly. Try this:

-(id) initWithButtons:(NSMutableArray*)buttonArray  {
    self = [super init];
    if (self) {
        [self setMenuButtons:buttonArray];
    }
}

You didn’t show how the menuButtons property is declared, but I assume it is:

@property (nonatomic, retain) NSArray* menuButtons;

This will retain menuButtons automatically for you whenever you set it with the setter. If you have your property declared like this:

@property (nonatomic, assign) NSArray* menuButtons;

then you need to retain the array manually:

-(id) initWithButtons:(NSMutableArray*)buttonArray  {
    self = [super init];
    if (self) {
        menuButtons = [buttonArray retain];
    }
}