ios - SLComposecontroller does not disable post button for long messages -

i used slcomposercontroller, not disabling post button when character count exceeds 140 character . want post url ,image , initial text on twitter via ios application. how this?

it user set correct length send, think won't send if long, or give callback if didn't work.

here did:

-(void) postontwitterinsideview:(uiviewcontroller *)viewcontroller                          message:(nsstring *)postmessage{      if( [slcomposeviewcontroller isavailableforservicetype:slservicetypetwitter] ){         slcomposeviewcontroller *twitterpost = [slcomposeviewcontroller                                                 composeviewcontrollerforservicetype:slservicetypetwitter];          [twitterpost setcompletionhandler:^(slcomposeviewcontrollerresult result){             switch (result) {                 case slcomposeviewcontrollerresultdone:                     // tell user message sent                     break;                  case slcomposeviewcontrollerresultcancelled:                     // tell user message not sent                     break;                 default:                     break;             }         }];          [twitterpost addimage:self.imagepost];         [twitterpost setinitialtext:postmessage];         [viewcontroller presentviewcontroller:twitterpost                                       animated:yes                                     completion:nil];     } else {         // tell user has activate service in settings of ios     } }