Question

I can’t work out what I am doing wrong with an NSMustableArray. It is fair to say that I don’t really understand memory allocation that well, so I apologize if this is a simple questions.

I have a tab bar application that is working well, and on one of the tab bars I have a front view and a back view of a person.

In the .h I have

@interface BurnsCalculatorViewController : UIViewController// <UIPickerViewDelegate, UIPickerViewDataSource>
{
    UIView              *frontView;
    UIView              *backView;
    UIButton            *frontButton;
    UIButton            *backButton;
    NSMutableArray      *frontBurnsArray;
}

@property (nonatomic, retain) UIView            *frontView;
@property (nonatomic, retain) UIView            *backView;
@property (nonatomic, retain) UIButton          *frontButton;
@property (nonatomic, retain) UIButton          *backButton;
@property (nonatomic, retain) NSMutableArray    *frontBurnsArray;

-(IBAction)frontButtonSelect:(id)sender;
-(IBAction)backButtonSelect:(id)sender;

@end

Then I have the .m file

@implementation BurnsCalculatorViewController

@synthesize frontView;
@synthesize backView;
@synthesize frontButton;
@synthesize backButton;
@synthesize frontBurnsArray;

-(IBAction)frontButtonSelect:(id)sender
{
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:1.0];
[UIView setAnimationTransition:UIViewAnimationTransitionFlipFromLeft forView:[self view] cache:YES];
    [self.view addSubview:backView];
    [self.view addSubview:backButton];
[UIView commitAnimations];
    NSLog(@"%@", frontBurnsArray);
}

-(IBAction)backButtonSelect:(id)sender
{
    [UIView beginAnimations:nil context:nil];
[UIView setAnimationDuration:1.0];
[UIView setAnimationTransition:UIViewAnimationTransitionFlipFromLeft forView:[self view] cache:YES];
    [self.view addSubview:frontView];
    [self.view addSubview:frontButton];
[UIView commitAnimations];
    NSLog(@"%@", frontBurnsArray);
}

-(void)viewDidLoad
{
    frontBurnsArray = [NSMutableArray arrayWithObjects: @"frontHead", @"frontChest", @"frontAbdomen", @"frontGroin",@"frontLeftArm", @"frontLeftForeArm", @"frontRightArm", @"frontRightForearm", @"frontLeftThigh", @"frontLeftLowerLeg", @"frontRightThigh", @"frontRightLowerLeg",nil];

    CGRect viewframe = CGRectMake(0, 0, 320, 480);
    frontView = [[UIView alloc] initWithFrame:viewframe];
    frontView.backgroundColor = [UIColor blueColor];
    [self.view addSubview:frontView];

    frontButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [frontButton addTarget:self action:@selector(frontButtonSelect:) forControlEvents:UIControlEventTouchDown];
    [frontButton setTitle:@"Show Back" forState:UIControlStateNormal];
    frontButton.frame = CGRectMake(210, 10, 100, 30);
    [self.view addSubview:frontButton];

    backView = [[UIView alloc] initWithFrame:viewframe];
    backView.backgroundColor = [UIColor blackColor];
    backButton = [[UIButton buttonWithType:UIButtonTypeRoundedRect] retain];
    [backButton addTarget:self action:@selector(backButtonSelect:)forControlEvents:UIControlEventTouchDown];
    [backButton setTitle:@"Show Front" forState:UIControlStateNormal];
    backButton.frame = CGRectMake(210, 10, 100, 30);
}

-(void)dealloc
{
    [super dealloc];
    [frontButton release];
    [backButton release];
    [frontBurnsArray release];
}
@end

What I can’t figure out is why the NSLogs in the IBActions are both telling me that the instance has been deallocated. Apart from the “release” in the dealloc, I am have said to retain the array and have not released it elsewhere.

I have spent ages searching for an answer to this, but just can’t figure it out.

Thanks!!

Answer 1

frontBurnsArray = [NSMutableArray arrayWithObjects: @"frontHead", @"frontChest", @"frontAbdomen", @"frontGroin",@"frontLeftArm", @"frontLeftForeArm", @"frontRightArm", @"frontRightForearm", @"frontLeftThigh", @"frontLeftLowerLeg", @"frontRightThigh", @"frontRightLowerLeg",nil];

You are not using the retaining property

try

self.frontBurnsArray = [NSMutableArray arrayWithObjects: @"frontHead", 
                                                         @"frontChest",
                                                         @"frontAbdomen", 
                                                         //....
                                                         nil];

You are creating an array, that is autorealesed, meaning it will disappear on the next run-loop. If you assign it to the property, it get automatically retained and will exists until you release it. you also could call

frontBurnsArray = [[NSMutableArray arrayWithObjects: @"frontHead", 
                                                         @"frontChest",
                                                         @"frontAbdomen", 
                                                         //....
                                                         nil] retain];