我想与facebook分享新闻。这是代码:RACSignal*sign=[RACSignalcreateSignal:^RACDisposable*(idsubscriber){if([[FBSDKAccessTokencurrentAccessToken]hasGranted:@"publish_actions"]){NSLog(@"1blck");NSLog(@"currtok?%@",[FBSDKAccessTokencurrentAccessToken]);[subscribersendNext:@YES];[subscribersendCompleted];}else{NSL