使用MFMailComposer时出现内存泄漏

Question

我正在尝试通过MfMail Composer发送CSV文件，一切正常，但使用Instruments时会出现很多泄漏。我无法找出我出了什么问题，这是我的代码。

-(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

我不能说我在您提供的代码中看到任何会导致您泄漏的内容。 您的泄漏可能发生在其他地方。

但是，我看到的是可能在-getCSV循环中创建许多自动释放的对象，并且这取决于您执行的迭代次数，这几乎是同样糟糕的。 按照您编写它的方式，每次迭代时，我都会看到一个日期格式化程序和三个用于主自动释放池的字符串。 一种建议是在循环外创建一个日期格式化程序，您可以在其中重复使用。 另一个建议是使用本地自动释放池来构建循环的胆量。 这样可以防止您的主自动释放池太大。

毫无疑问，您还应该考虑使用快速枚举。

这是应用了建议的循环：

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];
}