You can call the AppendObject operation of Object Storage Service (OSS) to append content to an appendable object. This is called append upload.

Usage notes

  • If the object to which you want to append content does not exist, an appendable object is created when you call the AppendObject operation.
  • When you call the AppendObject operation to append content to an object, you may encounter a few situations: If the object is an appendable object, and the specified position from which the append operation starts is equal to the current object length, the content is appended to the end of the object. If the specified position from which the append operation starts is not equal to the current object length, a PositionNotEqualToLength exception is thrown. If the object is not an appendable object, an ObjectNotAppendable exception is thrown.
  • The CopyObject operation cannot be performed on appendable objects.

Sample code

The following code provides an example on how to perform append upload:

OSSAppendObjectRequest * append = [OSSAppendObjectRequest new];
// Configure the required fields. bucketName indicates the name of the bucket. objectKey is equivalent to objectName that indicates the full path of the object you want to upload to OSS by using append upload. The path must include the extension of the object. For example, you can set objectKey to abc/efg/123.jpg. 
append.bucketName = @"<bucketName>";
append.objectKey = @"<objectKey>";
// Specify the position from which the first append operation starts. 
append.appendPosition = 0; 
NSString * docDir = [self getDocumentDirectory];
append.uploadingFileURL = [NSURL fileURLWithPath:@"<filepath>"];
// Configure the optional fields. 
append.uploadProgress = ^(int64_t bytesSent, int64_t totalByteSent, int64_t totalBytesExpectedToSend) {
    NSLog(@"%lld, %lld, %lld", bytesSent, totalByteSent, totalBytesExpectedToSend);
// append.contentType = @"";
// append.contentMd5 = @"";
// append.contentEncoding = @"";
// append.contentDisposition = @"";
OSSTask * appendTask = [client appendObject:append];
[appendTask continueWithBlock:^id(OSSTask *task) {
    NSLog(@"objectKey: %@", append.objectKey);
    if (!task.error) {
        NSLog(@"append object success!");
        OSSAppendObjectResult * result = task.result;
        NSString * etag = result.eTag;
        long nextPosition = result.xOssNextAppendPosition;
    } else {
        NSLog(@"append object failed, error: %@" , task.error);
    return nil;


For more information about the API operation that you can call to perform append upload, see AppendObject.