我想从使用AVCaptureDevice这样拍摄的图像的EXIF附件:NSMutableDictionary和CFDictionaryRef有什么区别?
CFDictionaryRef exifAttachments = (CFDictionaryRef)CMGetAttachment(buf, kCGImagePropertyExifDictionary, NULL);
NSMutableDictionary *exifAttachment = (__bridge NSMutableDictionary*)CMGetAttachment(buf, kCGImagePropertyExifDictionary, NULL);
似乎都返回相同的结果,虽然一个的NSMutableDictionary需要__bridge
投类型。他们之间有什么不同?我应该什么时候使用哪个?