NSMutableArray与NSMutableDictionary的一个奇怪问题

Question

我有一个XML解析器,它将XML文件中的所有信息(作为项目资源附加)解析为集合.我第一次通过NSMutableArray完成它,然后我将其转换为NSMutableDictionary,一切正常.在那之后,我意识到没有必要拥有NSMutableArray; 我只需要将XML直接解析为NSMutableDictionary.我做了它(它只是一个属性和我向对象添加一个对象的方式),但问题是我现在泄漏了.非常奇怪的泄漏.它可能发生而且不可能发生.每次它发生时都会说它有关于散列和键/值问题的东西.部分代码:

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict{
        self.currentElement = elementName;
        // category
        if(self.targetBranch==XML_KEY_CATEGORY && [elementName isEqualToString:XML_KEY_CATEGORY]) {
            self.categoryItem = [[CategoryItem alloc] initWithId:[attributeDict objectForKey:@"id"] andParentId:[attributeDict objectForKey:@"parentId"]];
            //NSLog(@"didStartElement with id %@",self.categoryItem.categoryId);
        }
    ...
        }

        - (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string{
        ...
            // categories
            if (self.targetBranch==XML_KEY_CATEGORY && [self.currentElement isEqualToString:XML_KEY_CATEGORY]) {
                //NSLog(@"adding category to array");
                if (self.categoryItem.categoryName)
                    self.categoryItem.categoryName = [NSString stringWithFormat:@"%@%@",self.categoryItem.categoryName,string]; //[string copy];
                else
                    self.categoryItem.categoryName = string; //[string copy];
        ...
        }


        - (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName{
            //NSLog(@"ended element: %@", elementName);

            // category
            if (self.targetBranch==XML_KEY_CATEGORY && [elementName isEqualToString:XML_KEY_CATEGORY]) {
                //NSLog(@"adding category to array");
                //[xmlParsedInfo addObject:self.categoryItem];
                //      if (self.categoryItem.categoryId && self.categoryItem.categoryId && self.categoryItem.categoryId!=NULL 
        //      && ![xmlParsedData objectForKey:self.categoryItem.categoryId]){
        //          //NSLog(@"adding dictionary element %@",self.categoryItem.categoryId);
        //          [xmlParsedData setObject:self.categoryItem forKey:self.categoryItem.categoryId];
                    [xmlParsedInfo addObject:self.categoryItem];

                }
        ...
        }

        -(NSDictionary*) getCategoriesForParentId:(NSString*)parentId_ fromUrl:(NSString *)strUrl{
            NSLog(@"getCategoriesForParentId: %@",parentId_);
            targetBranch = XML_KEY_CATEGORY;
            parentId = parentId_;
            xmlParsedInfo = [[NSMutableArray alloc] init];
        //  xmlParsedData = [[NSMutableDictionary alloc] init];
            [self parseXMLFileAtURL:strUrl];
            NSLog(@"category for parent id count is %i",xmlParsedInfo.count);
            //return xmlParsedData;
            NSDictionary *result = [self convertCategoryItemArrayToDictionary:xmlParsedInfo];
            [xmlParsedInfo release];
            return result; //[self convertCategoryItemArrayToDictionary:xmlParsedInfo];
        }

        - (NSDictionary *) convertCategoryItemArrayToDictionary:(NSMutableArray *)array 
        {
            NSMutableDictionary *mutableDictionary = [[NSMutableDictionary alloc] init];
            for (CategoryItem *catItem in array) {
                [mutableDictionary setObject:catItem forKey:catItem.categoryId];
            }
            return (NSDictionary *)[mutableDictionary autorelease];
        }

就像我说的那样,XML-parser工作得很好,而且还没有问题.但是你可以看到与字典相关的评论部分.在当前状态下它工作正常,但如果注释数组相关代码和UNcomment字典相关 - 它将泄漏.大部分时间我都会遇到2次泄漏:

#   Category    Event Type  Timestamp   RefCt   Address Size    Responsible Library Responsible Caller
0   CFBasicHash (key-store) Malloc  1928615936  1   0x9019600   512 MyApp   -[XMLParser parser:didEndElement:namespaceURI:qualifiedName:]
#   Category    Event Type  Timestamp   RefCt   Address Size    Responsible Library Responsible Caller
0   CFBasicHash (value-store)   Malloc  1928608768  1   0x900c600   512 MyApp   -[XMLParser parser:didEndElement:namespaceURI:qualifiedName:]

这些泄漏直接导致以下代码行:

        [xmlParsedData setObject:self.categoryItem forKey:self.categoryItem.categoryId];

那么这里的字典有什么问题？正如我可以看到它的哈希/密钥相关及其NSMutableDictionary内部问题.

我正在尝试使用模拟器的代码.所以我不能说这个问题是否仍然存在于真实设备中.也许它只是模拟器相关的bug(如键盘泄漏).
我正在解析的XML是静态的,它只是项目中的一个文件.此XML文件中有71个类别.因此,每个运行的应用程序都使用相同的数据执 这就是我说这个问题很奇怪的原因.在第一次使用泄漏监测器时,没有任何泄漏.在第二次尝试时它可能是1或2.所有下一次运行它不断显示2(如上所示)泄漏(+1导致字典本身,但这是由于其键或值泄漏,它只是链的一端) .

CategoryItem.h
@interface CategoryItem : NSObject {
    NSString * categoryName;
    NSString * categoryId;
    NSString * parentId;
}
@property (nonatomic,retain) NSString * categoryName; 
@property (nonatomic,retain) NSString * categoryId; 
@property (nonatomic,retain) NSString * parentId; 

- (id)init;
- (id)initWithId:(NSString *)id_ andParentId:(NSString *)parentId_;
- (id)initWithName:(NSString *)name_ andId:(NSString *)id_ andParentId:(NSString *)parentId_;
- (BOOL)isEqualToItem:(CategoryItem *)anItem;
- (NSUInteger)hash;

@end

CategoryItem.m

#import "CategoryItem.h"

@implementation CategoryItem

@synthesize categoryName; 
@synthesize categoryId; 
@synthesize parentId; 

-(id)init{
    self = [super init];
    return self;
}

-(id)initWithName:(NSString *)name_ andId:(NSString *)id_ andParentId:(NSString *)parentId_{
    self = [super init];
    if(self){
        self.categoryName = name_;
        self.categoryId = id_;
        self.parentId = parentId_;
    }
    return self;
}

-(id)initWithId:(NSString *)id_ andParentId:(NSString *)parentId_{
    self = [super init];
    if(self){
        self.categoryId = id_;
        self.parentId = parentId_;
    }
    return self;
}

- (void)dealloc {
    [categoryName release];
    [categoryId release];
    [parentId release];
    [super dealloc];
}

- (BOOL)isEqual:(id)other {
    if (other == self)
        return YES;
    if (!other || ![other isKindOfClass:[self class]])
        return NO;
    return [self isEqualToItem:other];
}

- (BOOL)isEqualToItem:(CategoryItem *)anItem {
    if (self == anItem)
        return YES;
    if (![(id) self.categoryName isEqual:anItem.categoryName])
        return NO;
    if (![(id) self.categoryId   isEqual:anItem.categoryId])
        return NO;
    if (![(id) self.parentId     isEqual:anItem.parentId])
        return NO;
    return YES;
}

- (NSUInteger)hash {
    NSString *string4Hash = [NSString stringWithFormat:@"%@%@%@",self.categoryName,self.categoryId,self.parentId];
    NSUInteger hash = [string4Hash hash];
    return hash;
}

@end

补充: 我找到的解决方案(对我来说是愚蠢的) - (NSDictionary*)getCategoriesForParentId:

归还这个:

    NSDictionary *result;

    result = (NSDictionary *)[xmlParsedData copy];
    [xmlParsedData release];

    return result;

!要么!

    return [(NSDictionary *)xmlParsedData autorelease];

}

所以重点是复制NSDictionaryMutable ......我只是想不通为什么它有帮助？!不保留但复制!调用getCategoriesForParentId()的方法需要NSDictionary(不是Mutable one).它通过alloc + init创建XMLParser,并在获取字典后释放创建的具有dealloc的XMLParser

- (void)dealloc {
    [currentElement release];
    [targetBranch   release];

    xmlParsedInfo = nil;
    xmlParsedData = nil; 
...

我还尝试返回类似(NSDictionary*)[xmlParsedData retain]或(NSDictionary*)xmlParsedData的内容,而没有额外的NSDictionary*结果 - 但是泄漏就在那里.

看起来问题是我没有使用xmlParsedData作为属性+ @ synthesize.所以现在我把它变成了一个属性(保留),并在dealloc中它现在[xmlParsedData发布]并且我从getCategoriesForParentId返回[xmlParsedData retain].它仍然泄漏.

Answer 1

您的代码似乎不使用ARC,但请在问题中指明.

每次进入你的if分支didStartElement并分配一个新元素时,你都会泄漏内存self.categoryItem.您正在分配一个新对象,但是当您将其分配给该属性时,它将在其上再发一个retain.下次分配下一个对象时,该属性将发出一个,release但是引用计数器仍然是一个必要的,因为你的alloc.

要使其正常工作,请在创建时或在将其分配给属性后发布自动释放:

self.categoryItem = [[[CategoryItem alloc] 
         initWithId:[attributeDict objectForKey:@"id"] 
        andParentId:[attributeDict objectForKey:@"parentId"]] autorelease];