Memory Leaks while using MFMailComposer - iphone

Question

I am trying to send a CSV file through MfMail Composer.Everything works fine but there are lot leaks while using Instruments.I am not able trace out where I went wrong.Here is my code.
-(NSData *)getCSV
{
NSManagedObjectContext *moc = [(ETAppDelegate *)[[UIApplication sharedApplication] delegate]managedObjectContext];
NSFetchRequest *request = [[[NSFetchRequest alloc]init]autorelease];
[request setEntity:[NSEntityDescription entityForName:#"Expense" inManagedObjectContext:moc]];
NSError *error = nil;
NSArray *results = [moc executeFetchRequest:request error:&error];
NSMutableArray *expensesList = [[[NSMutableArray alloc]init]autorelease];
for(int i = 0;i<[results count];i++){
NSString *category = [[results objectAtIndex:i]valueForKey:#"category"];
NSString *date = [[NSDateFormatter dateFormatterwithMediumStyle]stringFromDate:[[results objectAtIndex:i]valueForKey:#"date"]];
NSString *amount = [NSNumberFormatter localizedStringFromNumber:[[results objectAtIndex:i]valueForKey:#"amount"] numberStyle:NSNumberFormatterCurrencyStyle];
NSString *mailString = [NSString stringWithFormat:#"%#,%#,%#",category,date,amount ];
[expensesList addObject:mailString];
}
NSString *expensesString = [expensesList componentsJoinedByString:#"\n"];
NSData *expensesData = [expensesString dataUsingEncoding:NSUTF8StringEncoding];
return expensesData;
}
-(void)displayComposerSheet
{
NSData *csvFile = [self getCSV];
NSString *csvFileName = #"MyExpenses";
MFMailComposeViewController *mailController = [[MFMailComposeViewController alloc]init];
[mailController setSubject:#"List Of Expenses"];
[mailController setMessageBody:#"Expenses" isHTML:NO];
[mailController addAttachmentData:csvFile mimeType:#"text/csv" fileName:csvFileName];
[mailController setMailComposeDelegate:self];
[self presentModalViewController:mailController animated:YES];
[mailController release];
}

Answer 1

I can't say that I see anything in the code you've provided that should cause you to leak. Your leaks are likely taking place elsewhere.
What I do see, however, is the potential to create a lot of autoreleased objects in that loop in -getCSV, and depending on how many iterations you're performing, that could be almost as bad. The way you've written it, I see a date formatter and three strings headed for your main autorelease pool with every iteration. One suggestion is to create a date formatter outside your loop that you can reuse inside it. Another suggestion is to frame the guts of your loop with a local autorelease pool; that will prevent your main autorelease pool from becoming too large.
Apropos of nothing, you should also consider using fast enumeration.
Here's your loop with the suggestions applied:
NSDateFormatter *myDateFormatter = [NSDateFormatter dateFormatterWithMediumStyle];
NSMutableArray *expensesList = [[[NSMutableArray alloc] init] autorelease];
for (id obj in results)
{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
NSString *category = [obj valueForKey:#"category"];
NSString *date = [myDateFormatter stringFromDate:[obj valueForKey:#"date"]];
NSString *amount = [NSNumberFormatter localizedStringFromNumber:[obj valueForKey:#"amount"] numberStyle:NSNumberFormatterCurrencyStyle];
NSString *mailString = [NSString stringWithFormat:#"%#,%#,%#", category, date, amount];
[expensesList addObject:mailString];
[pool release];
}