Question

I am simple exporting my data into CSV file. But when I click on Export Button, Leak Instrument shows [NSPlaceholderMutableString init] error.

I have not used Placeholder anywhere in my NSMutableString, then What’s so wrong that Instrument shows Leak.

Here is my code:

- (IBAction)btnExportDataPressed:(id)sender
{
    csvString = [[NSMutableString alloc] init];
    csvString = [NSMutableString stringWithFormat:@"No.,Name,Type,MaskPAN,SwipeTime\n"];
    NSString *msg = @"";

    if (self.totalCards.count>0)
    {
        for (int i=0; i<self.totalCards.count; i++)
        {
            self.cardInfo = [self.totalCards objectAtIndex:i];
            [csvString appendString:[NSMutableString stringWithFormat:@"%d,%@ %@,%@,%@,%@\n",i+1,self.cardInfo.firstName,self.cardInfo.lastName,self.cardInfo.type,self.cardInfo.maskedPAN,self.cardInfo.swipeTime]];
        }
        NSLog(@"csvString:%@",csvString);

        NSFileManager *fileManager = [NSFileManager defaultManager];
        NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
        NSString *documentsDirectory = [paths objectAtIndex:0];
        NSString *fileName = [NSString stringWithFormat:@"ORANGE_BOWL_%@",[NSDate date]];

        NSString *fullPath = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.csv",fileName]];
        [fileManager createFileAtPath:fullPath contents:[csvString dataUsingEncoding:NSUTF8StringEncoding] attributes:nil];
        msg = @"Data exported successfully. Connect the device to iTunes to get the records.";
    }
    else
    {
        msg = @"No Data to Export";
    }

    [csvString release];        
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Discover Orange Bowl," message:msg delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
    [alert show];
    [alert release];
}

Below is error pic from Instrument

Answer 1

There’s a memory leak right at the top of your code:

csvString = [[NSMutableString alloc] init];
csvString = [NSMutableString stringWithFormat:@"No.,Name,Type,MaskPAN,SwipeTime\n"];

So you’re allocating memory for a mutable string (line 1) which inceases the retain count by 1, and then in line 2 you lose your pointer reference to that because you assign another string to the pointer. This will leak memory for sure; not sure if the rest of your code is doing anything else bad.

So delete the first line — it’s useless and only serves to cause a memory leak.

Also, your [csvString release] line looks wrong because when you last assigned something to csvstring you used [NSMutableString stringWithFormat] which doesn’t increase the retain count (and hence you shouldn’t decrease it by using release). So try removing the line that says [csvString release];.

The Leaks tool can show slightly baffling references to object you didn’t actually use; this is caused by these objects being used internally by objects that you did use (and leak).