修复内存泄漏iphone的麻烦

Question

我的应用程序中有 3 个内存泄漏，但我不知道如何修复它。我对xcode和objective c有点陌生。这是我的代码：

if(sqlite3_prepare_v2( [[DatabaseController sharedDatabaseController] getDb], sqlQueryConverted, -1, &dbStatement, NULL)==SQLITE_OK){

        //Run the query
        while ( sqlite3_step(dbStatement) == SQLITE_ROW ) 
        {    


            const char *name = (const char *)sqlite3_column_text(dbStatement, 0);
            int courseId = sqlite3_column_int(dbStatement, 1);
            const char *location = (const char *)sqlite3_column_text(dbStatement, 2);
            const char *date = (const char *)sqlite3_column_text(dbStatement, 3);

            //Convert the returnedElement char to string
            nameConverted = [[NSString alloc] initWithUTF8String:name];
            locationConverted = [[NSString alloc] initWithUTF8String:location];
            dateConverted = [[NSString alloc] initWithUTF8String:date];

            Course *course = [[[Course alloc]initWithName:nameConverted _id:courseId location:locationConverted courseDate:dateConverted] autorelease];

            //Add the course to the to a temporary list to remove duplicated items            
            [tempResults addObject:course];

        }  
        [nameConverted release];
        [locationConverted release];
        [dateConverted release];
    }

我也尝试过自动释放它。此代码用于过滤搜索并重新加载搜索显示表。如果我将release 行放在while 语句中，如果我输入2 个字母，应用程序就会崩溃。我该如何解决这个问题？

谢谢。

编辑：我一直在来回解决这个问题，但没有运气。我得出的结论是 Instruments 有问题，因为它仍然显示内存泄漏。这是今天的代码，我认为应该可以解决问题：

NSString *nameConverted = [[NSString alloc] initWithUTF8String:name];
            NSString *locationConverted = [[NSString alloc] initWithUTF8String:location];
            NSString *dateConverted = [[NSString alloc] initWithUTF8String:date];

            Course *course = [[[Course alloc]initWithName:nameConverted _id:courseId location:locationConverted courseDate:dateConverted] autorelease];

            //Add the course to the to a temporary list to remove duplicated items            
            [tempResults addObject:course];
            course = nil;
            [course release];
            [nameConverted release];
            nameConverted = nil;
            [locationConverted release];
            locationConverted = nil;
            [dateConverted release];
            dateConverted = nil;
            NSLog(@"course retain count %i",[course retainCount]);
            NSLog(@"name coverted retain count %i",[nameConverted retainCount]);
            NSLog(@"location coverted retain count %i",[locationConverted retainCount]);
            NSLog(@"date coverted retain count %i",[dateConverted retainCount]);

日志告诉我retainCount = 0;，所以我不明白为什么会有内存泄漏。大家能给我一些建议吗？

再次感谢。

Answer 1

您在每个循环中都在泄漏。你只发布了 3 last NSString。每次你为你的 3 个变量（nameConverted、locationConverted、dateConverted）重新分配一个新的 NSString 时，你也会失去对它们指向的 NSString 对象的引用。这意味着内存泄漏。当您退出 While 循环时，您只会释放其中的最后 3 个。

Answer 2

您在每个 while 循环中创建一个内存块，然后只释放一次。因此，如果您的 while 循环运行超过 10 次，则每个字符串的保留计数为 10，但仅释放一次。

要修复，请将您的 3 个版本放在您的 while 循环中，如下所示：

if(sqlite3_prepare_v2( [[DatabaseController sharedDatabaseController] getDb], sqlQueryConverted, -1, &dbStatement, NULL)==SQLITE_OK){

        //Run the query
        while ( sqlite3_step(dbStatement) == SQLITE_ROW ) 
        {    


            const char *name = (const char *)sqlite3_column_text(dbStatement, 0);
            int courseId = sqlite3_column_int(dbStatement, 1);
            const char *location = (const char *)sqlite3_column_text(dbStatement, 2);
            const char *date = (const char *)sqlite3_column_text(dbStatement, 3);

            //Convert the returnedElement char to string
            nameConverted = [[NSString alloc] initWithUTF8String:name];
            locationConverted = [[NSString alloc] initWithUTF8String:location];
            dateConverted = [[NSString alloc] initWithUTF8String:date];

            Course *course = [[[Course alloc]initWithName:nameConverted _id:courseId location:locationConverted courseDate:dateConverted] autorelease];

            //Add the course to the to a temporary list to remove duplicated items            
            [tempResults addObject:course];

        [nameConverted release];
        [locationConverted release];
        [dateConverted release];

        }  

    }

Answer 3

你试过用吗：

nameConverted = [[NSString initWithUTF8String:name] autorelease];
locationConverted = [[NSString initWithUTF8String:location] autorelease];
dateConverted = [[NSString initWithUTF8String:date] autorelease];

并删除循环外的版本？ 也不要自动删除课程对象，将其添加到 tempResults 后释放它。

Answer 4

这就是你应该这样做的方式。

NSString *nameConverted = [[NSString alloc] initWithUTF8String:name];
NSString *locationConverted = [[NSString alloc] initWithUTF8String:location];
NSString *dateConverted = [[NSString alloc] initWithUTF8String:date];

Course *course = [[Course alloc] initWithName:nameConverted _id:courseId location:locationConverted courseDate:dateConverted];
[tempResults addObject:course];
[course release];

[dateConverted release];
[locationConverted release];
[nameConverted release];