ios - 重新加载对象时 NSMutableArray 内存泄漏

Question

我正在使用 Three20/TTThumbsviewcontroller 加载照片。很长一段时间以来，我一直在努力解决设置照片源时的内存泄漏问题。我是 Object C 和 iOS 内存管理的初学者。请查看以下代码，并提出任何明显的错误或声明和释放变量的任何错误。

-- PhotoViewController.h

 @interface PhotoViewController : TTThumbsViewController <UIPopoverControllerDelegate,CategoryPickerDelegate,FilterPickerDelegate,UISearchBarDelegate>{
......
NSMutableArray *_photoList;

......
@property(nonatomic,retain) NSMutableArray *photoList;

-- PhotoViewController.m

@implementation PhotoViewController
....

@synthesize photoList;
.....

- (void)LoadPhotoSource:(NSString *)query:(NSString *)title:(NSString* )stoneName{


NSLog(@"log- in loadPhotosource method");


if (photoList == nil)
    photoList = [[NSMutableArray alloc] init ];

[photoList removeAllObjects];



@try {
    sqlite3 *db;
    NSFileManager *fileMgr = [NSFileManager defaultManager];
    NSString* documentsPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];

    NSString *dbPath = [documentsPath stringByAppendingPathComponent: @"DB.s3db"];
    BOOL success = [fileMgr fileExistsAtPath:dbPath];
    if(!success)
    {
        NSLog(@"Cannot locate database file '%@'.", dbPath);
    }

    if(!(sqlite3_open([dbPath UTF8String], &db) == SQLITE_OK))
    {
        NSLog(@"An error has occured.");
    }


    NSString *_sql = query;
    const char *sql = [_sql UTF8String];
    sqlite3_stmt *sqlStatement;
    if(sqlite3_prepare(db, sql, -1, &sqlStatement, NULL) != SQLITE_OK)
    {
        NSLog(@"Problem with prepare statement");
    }

    if ([stoneName length] != 0)
    {
        NSString *wildcardSearch = [NSString stringWithFormat:@"%@%%",[stoneName stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]];

        sqlite3_bind_text(sqlStatement, 1, [wildcardSearch UTF8String], -1, SQLITE_STATIC);
    }


    while (sqlite3_step(sqlStatement)==SQLITE_ROW) {

        NSString* urlSmallImage = @"Mahallati_NoImage.png";
        NSString* urlThumbImage = @"Mahallati_NoImage.png";


        NSString *designNo = [NSString stringWithUTF8String:(char *) sqlite3_column_text(sqlStatement,2)];
        designNo = [designNo stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

        NSString *desc = [NSString stringWithUTF8String:(char *) sqlite3_column_text(sqlStatement,7)];
        desc = [desc stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

        NSString *caption = designNo;//[designNo stringByAppendingString:desc];
        caption = [caption stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];



        NSString *smallFilePath = [documentsPath stringByAppendingPathComponent: [NSString stringWithFormat:@"Small%@.JPG",designNo] ];
        smallFilePath = [smallFilePath stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
        if ([fileMgr fileExistsAtPath:smallFilePath]){
            urlSmallImage = [NSString stringWithFormat:@"Small%@.JPG",designNo];
        }

        NSString *thumbFilePath = [documentsPath stringByAppendingPathComponent: [NSString stringWithFormat:@"Thumb%@.JPG",designNo] ];
        thumbFilePath = [thumbFilePath stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

        if ([fileMgr fileExistsAtPath:thumbFilePath]){
            urlThumbImage = [NSString stringWithFormat:@"Thumb%@.JPG",designNo];
        }




        NSNumber *photoProductId = [NSNumber numberWithInt:(int)sqlite3_column_int(sqlStatement, 0)];
        NSNumber *photoPrice = [NSNumber numberWithInt:(int)sqlite3_column_int(sqlStatement, 6)];

        char *productNo1 = sqlite3_column_text(sqlStatement, 3);
        NSString* productNo;
        if (productNo1 == NULL)
            productNo = nil;
        else
            productNo = [NSString stringWithUTF8String:productNo1];

        Photo *jphoto = [[[Photo alloc] initWithCaption:caption
                                               urlLarge:[NSString stringWithFormat:@"documents://%@",urlSmallImage] 
                                               urlSmall:[NSString stringWithFormat:@"documents://%@",urlSmallImage] 
                                               urlThumb:[NSString stringWithFormat:@"documents://%@",urlThumbImage]
                                                   size:CGSizeMake(123, 123) 
                                              productId:photoProductId
                                                  price:photoPrice
                                            description:desc
                                               designNo:designNo 
                                              productNo:productNo
                          ]  autorelease];



        [photoList addObject:jphoto];
        [jphoto release];



    }


}
@catch (NSException *exception) {
    NSLog(@"An exception occured: %@", [exception reason]);
}



self.photoSource = [[[MockPhotoSource alloc]
                     initWithType:MockPhotoSourceNormal
                     title:[NSString stringWithFormat: @"%@",title]
                     photos: photoList
                     photos2:nil] autorelease];

}

使用不同的查询再次调用上述 LoadPhotosource 方法时会发生内存泄漏...我觉得声明 NSMutableArray (photoList) 有问题，但无法弄清楚如何修复内存泄漏。非常感谢任何建议。

Answer 1

我没有在您的代码中看到任何泄漏的对象，但实际上是双重释放的对象，最终会使您的应用程序崩溃:

在你的最后几行中，你有这个:

Photo *jphoto = [[[Photo alloc] initWithCaption:caption
                                               urlLarge:[NSString stringWithFormat:@"documents://%@",urlSmallImage] 
                                               urlSmall:[NSString stringWithFormat:@"documents://%@",urlSmallImage] 
                                               urlThumb:[NSString stringWithFormat:@"documents://%@",urlThumbImage]
                                                   size:CGSizeMake(123, 123) 
                                              productId:photoProductId
                                                  price:photoPrice
                                                description:desc
                          designNo:designNo 
                                              productNo:productNo
                          ]  autorelease];



        [photoList addObject:jphoto];
        [jphoto release];

如果你仔细观察，你有一个双重释放(alloc 中的自动释放和 addObject 之后的释放)。您应该删除其中一个。

除此之外，我还向您推荐一些东西:

1. 切换到 ARC:如果您是新手，您肯定会利用它，因为您将不必再担心几乎所有的内存管理。您的代码将没有泄漏的对象和内存崩溃。只需注意内存保留周期和变量所有权即可。

2. 删除 NSMutableArray *_photoList;，您没有使用它，因为您将属性合成器声明为 @synthesize photoList;。此外，正如罗伯特在下面评论的那样，您应该在使用该属性时使用这种形式来明确区分:@synthesize photoList = photoList_;下划线放在最后更好，因为 Apple 在开头使用它，您不想不小心使用相同的变量名。

3. 使用属性访问器来管理 ivar。而不是这样做:

   如果(照片列表 == 无)
photoList = [[NSMutableArray alloc] init ];

试试这个:

if (photoList == nil)
    self.photoList = [[[NSMutableArray alloc] init] autorelease];

在您的示例中，两行具有相同的行为，但第二行更可取，因为它将依赖于您的可变内存策略。如果你有一天通过副本或分配更改你的保留，你的代码仍然可以毫无问题地工作。以同样的方式，通过为你的 ivar 分配一个 nil 来释放你的内存 self.photoList = nil

为什么你认为你有泄漏的对象？