Question

I’m subclassing UINavigationController and UITableview and for some reason, my views are leaking memory, although I’ve implemented all of the proper methods and release calls. When I use the native class instead of a subclass, everything works just fine, without leaking.

EDIT:

Here’s my superclass header:

//
//  MBAbstractViewController.h
//  GabbaiHD
//
//  Created by Moshe Berman on 11/24/10.
//  Copyright 2010 MosheBerman.com. All rights reserved.
//

#import <UIKit/UIKit.h>


@interface MBAbstractViewController : UIViewController {
    IBOutlet UIImageView *backgroundImageView;
    NSString *announcementText;
}

@property (nonatomic, retain) NSString *type;
@property (nonatomic, retain) NSDictionary *options;
@property (nonatomic, retain) NSString *announcementText;

-(void) setAnnouncementText:(NSString *)text;

@end

Superclass implementation:

//
//  MBAbstractViewController.m
//  GabbaiHD
//
//  Created by Moshe Berman on 11/24/10.
//  Copyright 2010 MosheBerman.com. All rights reserved.
//

#import "MBAbstractViewController.h"


@implementation MBAbstractViewController

@synthesize type, options, announcementText;

 // The designated initializer.  Override if you create the controller programmatically and want to perform customization that is not appropriate for viewDidLoad.
/*
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization.
    }
    return self;
}
*/

/*
// Implement loadView to create a view hierarchy programmatically, without using a nib.
- (void)loadView {
}
*/

// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
    [super viewDidLoad];
    UIColor *clearColor = [[UIColor alloc] colorWithAlphaComponent:0.0];
    [self.view setBackgroundColor: clearColor];
    [clearColor release];
}


- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
    if(interfaceOrientation == UIInterfaceOrientationLandscapeLeft ||  interfaceOrientation == UIInterfaceOrientationLandscapeRight){
        return YES;
    }else{
        return NO;
    }
}

- (void)didReceiveMemoryWarning {
    // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];

    // Release any cached data, images, etc. that aren't in use.
}


- (void)viewDidUnload {
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;

}


- (void)dealloc {
    [announcementText release];
    [options release];
    [type release];
    [super dealloc];
}


@end

Here’s my subclass header:

//
//  MBAnnouncementViewController.h
//  GabbaiHD
//
//  Created by Moshe Berman on 11/24/10.
//  Copyright 2010 MosheBerman.com. All rights reserved.
//

#import <UIKit/UIKit.h>
#import "MBAbstractViewController.h"

@interface MBAnnouncementViewController : MBAbstractViewController {
    IBOutlet UILabel *announcement;
}

- (void) setAnnouncementText:(NSString *)text withSize:(CGFloat)size;

@end

and the subclass implementation:

        //
//  MBAnnouncementViewController.m
//  GabbaiHD
//
//  Created by Moshe Berman on 11/24/10.
//  Copyright 2010 MosheBerman.com. All rights reserved.
//

#import "MBAnnouncementViewController.h"
#import "Constants.h"[

@implementation MBAnnouncementViewController

 // The designated initializer.  Override if you create the controller programmatically and want to perform customization that is not appropriate for viewDidLoad.
/*
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization.
    }
    return self;
}
*/


// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
    [super viewDidLoad];

    [announcement setText:announcementText]; 

    UIImage *slideImage = [[UIImage alloc] initWithContentsOfFile:[[NSBundle mainBundle] pathForResource:[[NSString stringWithFormat:@"%@_slide", kTheme]description] ofType:@"png"]];  
    [backgroundImageView setImage:slideImage];
    [slideImage release];   


}



- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
    // Overriden to allow any orientation.
    return YES;
}


- (void)didReceiveMemoryWarning {
    // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];

    // Release any cached data, images, etc. that aren't in use.
}

- (void) setAnnouncementText:(NSString *)text withSize:(CGFloat)size{
    UIFont *font = [[UIFont alloc] fontWithSize:size];
    [announcement setFont:font];
    [font release];
    [announcement setText:text];

}

- (void)viewDidUnload {
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}


- (void)dealloc {
    [announcementText release];
    [super dealloc];
}


@end

What could be causing memory leaks in a subclass? Am I missing something? (There is more relevant code here.)

Answer 1

You should not be alloc’ing UIColor in this way:

[[UIColor alloc] colorWithAlphaComponent:0.0];

You’ve alloc’d the instance without initializing it, then you’ve called a factory method and lost the reference to the instance you alloc’d.

You’ll want to call one of the initializers before calling colorWithAlphaComponent:. I’m not sure what the behaviour will be if you don’t do so. Why not just [UIColor clearColor];?

You’re making the same mistake with UIFont too:

UIFont *font = [[UIFont alloc] fontWithSize:size];

You should never do this. The only methods you chain onto +alloc should be initializers (which always return whatever was alloc’d). You’re leaking here, and also getting some weird unintended behaviour I dare say.

Also, as David Liu says, you appear to be over-releasing announcementText and under-releasing announcement, which will cause both a crash and a leak, depending on how lucky you get.

EDIT | Based on your update that shows your header files, there are further issues (not specifically related to leaks).

@property (nonatomic, retain) NSString *announcementText;

You should never retain NSString*; instead you should copy it.

@property (nonatomic, copy) NSString *announcementText;

This is because NSString* might actually be a mutable string and be changed later. You may use retain if you’re specifically wanting this however.

You also do not need to expressly declare -setAnnouncementText: when you have the @property announcementText.

In your subclass setAnnouncementText:withSize: actually does nothing to the announcementText ivar, which is confusing I guess. You’ll want to release the announcement ivar and fix the issue with UIColor and UIFont being used incorrectly (which are leaking).