Question

I’m kinda new in finding memory leaks in objective c and how to fix them. I’m know how to use alloc/init/copy and release/retain but ( a least i think so 🙂 ) but i have some strange memory leaks in my IOS app.

-(void) sendStats {

// read the app settings
plistHandler *readData  = [[plistHandler alloc] init];
[readData setPlistName:@"Settings"];
NSDictionary *settingsArray  = [readData readPlist];
[readData release];

NSNumberFormatter * f = [[NSNumberFormatter alloc] init];
[f setNumberStyle:NSNumberFormatterDecimalStyle];
NSNumber * myNumber = [f numberFromString:[NSString stringWithFormat:@"%@", [settingsArray objectForKey:@"range"]]];
[f release];

int rangeForUrl;

if(myNumber != nil) {
    rangeForUrl = [myNumber intValue];
} else {
    rangeForUrl = 10;
}

// get uniqe device ID
UIDevice *getdev = [UIDevice currentDevice];
NSString *uniqueIdentifier = [getdev uniqueIdentifier];

NSString *deviceId  = [NSString stringWithFormat:@"IOS-%@", uniqueIdentifier];

// get the unix timestamp
NSDate * past = [NSDate date];
NSTimeInterval oldTime = [past timeIntervalSince1970]; 
NSString * unixTime = [[[NSString alloc] initWithFormat:@"%0.0f", oldTime] autorelease];


// send the data with a post request to the API
HttpRequest *data = [[HttpRequest alloc] init];
data.postData   = [NSString stringWithFormat:@"&device=%@&age=%@&gender=%@&latitude=%@&longitude=%@&timestamp=%@", deviceId, [settingsArray objectForKey:@"age"], [settingsArray objectForKey:@"gender"], @"00", @"00", unixTime];

data.controller = @"sendDevice";

NSString *url   = [NSString stringWithFormat:@"http://www..eu/api/send_device"];

[data loadHostName:url];

[data release];

//NSLog(@"string s: %@", data.postData);

}

This is the memory leak according to Xcode instruments => leaks:

Leaked Object # Address Size Responsible Library Responsible Frame
NSCFString, 0x16cb40 144 Bytes Foundation -[NSPlaceholderString initWithFormat:locale:arguments:]

This is the line with “data.postData = …” in my code. Can someone help me out?

this is how I use postData in the class httpRequest:

- (void)loadHostName:(NSString *)hostName {



responseData = [[NSMutableData alloc] init];
NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:@"%@", hostName]];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];

if(authString) {
    [request setValue:authString forHTTPHeaderField:@"Authorization"];
}

if([postData isKindOfClass:[NSString class]] && postData != @"") {

    NSData *dataToPost = [postData dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];
    NSString *postLength = [NSString stringWithFormat:@"%d",[dataToPost length]];
    [request setHTTPMethod:@"POST"];
    [request setValue:postLength forHTTPHeaderField:@"Content-Length"];
    [request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Current-Type"];
    [request setHTTPBody:dataToPost];

}

NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
[connection release];

}

with of course:

NSString *postData;
@property (nonatomic, retain) NSString *postData;

and

@synthesize postData;

Answer 1

You need to release postData in dealloc.

looks like its fixed now. But i dont really understand how the dealloc works. I never did a
alloc/init on postData. Does this mean every object in my .h file like
postData need to be released in the dealloc in the .m file?

Speaking of properties, you need to release in dealloc all your properties not marked assign (along with any non-property instance variable you own). Non-assign properties own the object held by the backing instance variable so you need to relinquish ownership of it by sending it a release message in dealloc.

From “The Objective-C Programming Language”:

Declared properties, along with the @synthesize directive, take the
place of accessor method declarations; when you synthesize a property,
the compiler creates accessor methods as needed. However, there is no
direct interaction between property declaration and the dealloc
method—properties are not automatically released for you. Declared
properties do, however, provide a useful way to cross-check the
implementation of your dealloc method: you can look for all the
property declarations in your header file and make sure that object
properties not marked assign are released, and those marked assign are
not released.

I would also recommend you to read the “Memory Management Programming Guide”.