objective-c - 处理 NSJSONSerialization 中的 Foundation 对象时发生内存泄漏

Question

我正在努力修复我制作的辅助函数中的内存泄漏。辅助函数获取

的结果

+ (id)JSONObjectWithData:(NSData *)data options:(NSJSONReadingOptions)opt error:(NSError * _Nullable *)error 

并将所有叶子元素转换为 NSString(如果它们是 NSNumber)。

方法如下:

-(NSArray *) stringisizeObjects:(NSArray *)inputArray{
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    NSMutableArray *mutable = [[NSMutableArray alloc] initWithCapacity:[inputArray count]];

    for (int i = 0; i < [inputArray count]; i++) {
        NSArray *keys = [inputArray[i] allKeys];

        NSMutableDictionary *addDictionary = [[NSMutableDictionary alloc] initWithCapacity:[keys count]];

        for (int j = 0; j < [keys count]; j++) {

            id theObject = [[inputArray[i] objectForKey:keys[j]]autorelease];

            if ([theObject isKindOfClass:[NSNumber class]]) {

                [addDictionary setObject:[theObject stringValue] forKey:keys[j]];
                [theObject release];

            }else if ([theObject isKindOfClass:[NSString class]]){
                [addDictionary setObject:[inputArray[i] objectForKey:keys[j]] forKey:keys[j]];
            }

        }
        [mutable addObject:addDictionary];
    }
    NSArray *returnArray = [mutable copy];

    [mutable removeAllObjects];
    [mutable release];
    [pool drain];
    return returnArray;
}

这是我获取输入数组的方法。

id parsedThingy = [NSJSONSerialization JSONObjectWithData:resultJSONData options:1 error:&jsonDecodeError];

在将结果传递给 stringisize 方法之前，我必须确保我有一个带有匹配键的 NSDictionaries 的 NSArray。

NSArray *resultArray = [self stringisizeObjects:parsedThingy];

X-Code 内存泄漏工具已指出此方法是导致问题的原因。

Instruments showing leaks

正如你所看到的，我尝试将东西包装在自动释放池中，自动释放和释放。我只是看不到任何前进的方向。

这是一个 24/7 运行的非 ARC 项目。

编辑:我听取了 Droppy 的建议并尝试使用 mutableCopy 重写该方法。泄漏仍然存在。此时，我唯一的解决方法可能是更改 JSON 的源以仅发送字符串。 :(

-(NSArray *) stringisizeObjects2:(NSArray *)inputArray{
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    NSMutableArray *mutableArray = [inputArray mutableCopy];

    for (int i = 0; i < [mutableArray count]; i++) {
        NSMutableDictionary *mutableDict = [mutableArray[i] mutableCopy];
        NSArray *keys = [mutableDict allKeys];

        for (int j = 0; j < [keys count]; j++) {
            if ([[mutableDict objectForKey:keys[j]] isKindOfClass:[NSNumber class]]) {
                NSString *stringValue = [[mutableDict objectForKey:keys[j]] stringValue];

                [mutableDict removeObjectForKey:keys[j]];
                [mutableDict setObject:stringValue  forKey:keys[j]];
            }
        }
        mutableArray[i] = [mutableDict copy];
        [mutableDict release];
    }

    NSArray *returnArray = [mutableArray copy];

    [mutableArray release];
    [pool drain];
    return returnArray;
}

Answer 1

问题:

1. addDictionary 调用了 alloc 但未调用 release 或 autorelease
2. returnArray = [可变副本];//确实增加了retainCount +1，这里需要autorelease
3. id theObject = [inputArray[i] objectForKey:keys[j]];//不需要自动释放或释放不属于您的对象
4. 将 NSAutoreleasePool 添加到此处的顶部和底部，什么也不做

解决方案:

-(NSArray *) stringisizeObjects:(NSArray *)inputArray{
    NSMutableArray *mutable = [[NSMutableArray alloc] initWithCapacity:[inputArray count]];

    for (int i = 0; i < [inputArray count]; i++) {
        NSArray *keys = [inputArray[i] allKeys];

        NSMutableDictionary *addDictionary = [[NSMutableDictionary alloc] initWithCapacity:[keys count]];

        for (int j = 0; j < [keys count]; j++) {

            id theObject = [inputArray[i] objectForKey:keys[j]]; // not need autorelease

            if ([theObject isKindOfClass:[NSNumber class]]) {

                [addDictionary setObject:[theObject stringValue] forKey:keys[j]];
                //[theObject release]; // not need release value here

            }else if ([theObject isKindOfClass:[NSString class]]){
                [addDictionary setObject:[inputArray[i] objectForKey:keys[j]] forKey:keys[j]];
            }

        }
        [mutable addObject:addDictionary];
        [addDictionary release]; // release after not use
    }
    NSArray *returnArray = [[[NSArray alloc] initWithArray:mutable] autorelease]; // auto release for return value

    [mutable removeAllObjects];
    [mutable release];
    return returnArray;
}