自iOS8以来，无法加载图像属性，如EXIF

我的代码在iOS7.x上运行得很好。但由于我是为iOS8编译的，它不再检索基本信息以外的其他信息。这是我现在得到的唯一信息，没有更多的日期、艺术家、模特等：

{
    ColorModel = RGB;
    DPIHeight = 72;
    DPIWidth = 72;
    Depth = 8;
    Orientation = 1;
    PixelHeight = 2448;
    PixelWidth = 3264;
    "{Exif}" =     {
        ColorSpace = 1;
        PixelXDimension = 3264;
        PixelYDimension = 2448;
    };
    "{JFIF}" =     {
        DensityUnit = 1;
        JFIFVersion =         (
            1,
            0,
            1
        );
        XDensity = 72;
        YDensity = 72;
    };
    "{TIFF}" =     {
        Orientation = 1;
    };
}

我的代码如下：

-(NSDictionary*)getExif:(NSURL*)assetURL asset:(ALAssetRepresentation *)image_representation {
    // create a buffer to hold image data
    uint8_t *buffer = (Byte*)malloc(image_representation.size);
    NSUInteger length = [image_representation getBytes:buffer fromOffset: 0.0  length:image_representation.size error:nil];

    if (length != 0)  {

        // buffer -> NSData object; free buffer afterwards
        NSData *adata = [[NSData alloc] initWithBytesNoCopy:buffer length:image_representation.size freeWhenDone:YES];

        // identify image type (jpeg, png, RAW file, ...) using UTI hint
        NSDictionary* sourceOptionsDict = [NSDictionary dictionaryWithObjectsAndKeys:(id)[image_representation UTI],kCGImageSourceTypeIdentifierHint,nil];

        // create CGImageSource with NSData
        CGImageSourceRef sourceRef = CGImageSourceCreateWithData((__bridge CFDataRef) adata,
                                                                 (__bridge CFDictionaryRef) sourceOptionsDict);

        // get imagePropertiesDictionary
        CFDictionaryRef imagePropertiesDictionary = CGImageSourceCopyPropertiesAtIndex(sourceRef,0, NULL);
        NSLog(@"image props: %@",imagePropertiesDictionary);

        CFDictionaryRef propsRef = (CFDictionaryRef)CFDictionaryGetValue(imagePropertiesDictionary, @"{TIFF}");
        NSDictionary *props = (__bridge NSDictionary*)propsRef;

        NSMutableDictionary *d = [[NSMutableDictionary alloc] init];

        NSString * make = nil;
        NSString *model = nil;

        NSString *
        s =         [props objectForKey:@"DateTime"   ]; if (s) [d setObject: s                    forKey:@"DateTime"];
        s =         [props objectForKey:@"Artist"     ]; if (s) [d setObject:[s capitalizedString] forKey:@"Artist"];

        s = make  = [props objectForKey:@"Make"       ]; if (s) [d setObject:s                     forKey:@"Make"];
        s = model = [props objectForKey:@"Model"      ]; if (s) {
            if (make ) s = [s stringByReplacingOccurrencesOfString:make  withString:@""];
            [d setObject:s forKey:@"Model"];
        }
        // etc.

我认为这是Photos.Framework的一个bug。因为我在获取所有相集时可以获得完整的元数据，但在按集合获取相集时丢失了一些信息