ios sdk的一个报错，小白请教

用的是demo里的代码



// 异步上传
- ( void)uploadObjectAsync {
    OSSPutObjectRequest * put = [OSSPutObjectRequest new ];


    // required fields
    put. bucketName = @"gogogame-sh" ;
    put. objectKey = @"lkmtest";
     NSString * docDir = [ self getDocumentDirectory];
    put. uploadingFileURL = [ NSURL fileURLWithPath :[docDir stringByAppendingPathComponent : @"file10m" ]];
    // optional fields
    put. uploadProgress = ^( int64_t bytesSent, int64_t totalByteSent, int64_t totalBytesExpectedToSend) {
         NSLog( @"%lld, %lld, %lld", bytesSent, totalByteSent, totalBytesExpectedToSend);
    };
    put. contentType = @"";
    put. contentMd5 = @"";
    put.contentEncoding = @"" ;
    put.contentDisposition = @"" ;


     OSSTask * putTask = [ client putObject:put];


    [putTask continueWithBlock:^ id( OSSTask *task) {
         NSLog( @"objectKey: %@", put. objectKey);
         if (!task. error) {
             NSLog (@"upload object success!" );
        } else {
             NSLog (@"upload object failed, error: %@" , task. error );
        }
         return nil;
    }];
}
最后报了

2016-04-30 18:24:43.797 oss_ios_demo[2297:1907] upload object failed, error: Error Domain=com.aliyun.oss.clientError Code=8 "The operation couldn’t be completed. (com.aliyun.oss.clientError error 8.)" UserInfo=0x1453e790 {ErrorMessage=Catch exception - *** setObjectForKey: object cannot be nil (key: x-oss-security-token)}