ios 获取文件的mimeType

+ (NSString*)mimeTypeOfFileAtPath: (NSString *) path {
    NSURL* fileUrl = [NSURL fileURLWithPath:path];
    NSString * extension = [fileUrl pathExtension];
    NSString *UTI = (__bridge_transfer NSString *)UTTypeCreatePreferredIdentifierForTag(kUTTagClassFilenameExtension, (__bridge CFStringRef)extension, NULL);
    NSString *contentType = (__bridge_transfer NSString *)UTTypeCopyPreferredTagWithClass((__bridge CFStringRef)UTI, kUTTagClassMIMEType);
    if (!contentType) {
        return @"application/octet-stream";
    } else {
        return contentType;
    }
}