Memory Leak in returning NSMutableArray from class

Question

Hi

I am quite new to Objective C for the iPhone, so I hope you wont kill me for asking a simple question.

I have made an App that works fine, except that Instruments reports memory leaks from the class below. I use it to store settings from one class and then retrieve them from another class. These settings are stored on a file so they can be retrieved every time the App is ran.

What can I do do release the "setting" and is there anything that can be done to call (use) the class in a smarter way?

Thanks

----- Below is Settings.m -----

#import "Settings.h"

@implementation Settings

@synthesize settings;

-(NSString *)dataFilePath  // Return path for settingfile, including filename
{
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];

    return [documentsDirectory stringByAppendingPathComponent:kUserSettingsFileName];
}

-(NSMutableArray *)getParameters  // Return settings from disk after checking if file exist (if not create with default values)
{
    NSString *filePath = [self dataFilePath];

    if ([[NSFileManager defaultManager] fileExistsAtPath:filePath]) // Getting data from file
    {
        settings = [[NSMutableArray alloc] initWithContentsOfFile:filePath];
    }

    else // Creating default settings

    {   
        settings = [[NSMutableArray alloc] initWithObjects:
                        [NSNumber numberWithInteger:50],        
                        [NSNumber numberWithInteger:50],        
                        nil];

        [settings writeToFile:[self dataFilePath] atomically:YES];

    }
    return settings;
}


    ----- Below is my other class from where I call my Settings class -----

    // Get settings from file
    Settings *aSetting = [[Settings alloc] init];

    mySettings = [aSetting getParameters];
    [aSetting release];

Answer 1

In your -getParameters method you alloc/init an NSMutableArray ([[NSMutableArray alloc] initWithContentsOfFile:filePath] - i.e. retain count of 1) which you never release. You should autorelease your array before returning it: return [settings autorelease].

Note that if you need to put the setting parameters in your mySettings variable and want to keep it around, you should do mySettings = [[aSetting getParameters] retain]; so that the retain count does not drop to 0.

Answer 2

Or, better yet:

1. declare the settings property as a retaining property, then
2. use self.settings instead of settings in your -getParameters method, and finally
3. call autorelease on your arrays right after alloc/initting them.

Answer 3

Hi

Managed to solve the Settings class by modifying two lines:

1: Using settings = [NSMutableArray arrayWithContentsOfFile:filePath] instead of settings = [[NSMutableArray alloc] initWithContentsOfFile:filePath]

2: In a similar way using settings = [NSMutableArray arrayWithObjects: instead of settings = [[NSMutableArray alloc] initWithObjects

Now I only have to solve the leak I have when I create these from another class. Any ideas how?