Post on wall, but i don't see any attachment. Why?

Why don't I see @"The Facebook Running app" caption 开发者_如何学运维? I use the facebook connect sample.

-(IBAction)publishStream:(id)sender {
       SBJSON *jsonWriter = [[SBJSON new] autorelease];

  NSDictionary* actionLinks = [NSArray arrayWithObjects:[NSDictionary dictionaryWithObjectsAndKeys:
                               @"Always Running",@"text",@"http://itsti.me/",@"href", nil], nil];

  NSString *actionLinksStr = [jsonWriter stringWithObject:actionLinks];   
  NSDictionary* attachment = [NSDictionary dictionaryWithObjectsAndKeys:
                               @"a long run", @"name",
                               @"The Facebook Running app", @"caption",
                               @"it is fun", @"description",
                               @"http://itsti.me/", @"href", nil];   
  NSString *attachmentStr = [jsonWriter stringWithObject:attachment];   
  NSMutableDictionary* params = [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                 @"Head",  @"user_message_prompt",
                                 actionLinksStr, @"action_links",
                                 attachmentStr, @"attachment",
                                 nil];

  [_facebook dialog:@"feed"
          andParams:params
        andDelegate:self]; 
}

I commented out the action links and attachment parts in the demo & the call to _facebook dialog works just the same. I don't think a call to the dialog is using those parts. I'm in the source code now having a look because there's a current facebook dialog problem out there.