使用MFMailComposer时出现内存泄漏

Question

我想通过MfMail Composer发送一个CSV文件。一切正常，但使用Instruments时出现很多泄漏。我无法找到我出错的地方。这里是我的代码。

-(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

我不能说我看到你提供的代码中的任何东西都会导致你泄漏。你的泄漏可能发生在别处。

我所看到的，然而，在-getCSV创建在循环自动释放的对象很多的潜力，这取决于您要执行多少次迭代，这可能是几乎一样糟糕。按照您写它的方式，我会看到一个日期格式化程序和三个字符串，每次迭代都会前往主自动释放池。一个建议是在你的循环之外创建一个日期格式化器，你可以在其中重用。另一个建议是用本地自动释放池构建循环的内核;这将防止你的主autorelease池变得太大。

没有任何意思，你也应该考虑使用快速枚举。

这是你的循环应用了建议：

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]; 
}