NSString *requestString = (self.isFirstTimeDownload) ? [NSString stringWithFormat:[self.commonModel.apiURLs objectForKey:@"updateNewsVerPOST"],@""] : [NSString stringWithFormat:[self.commonModel.apiURLs objectForKey:@"updateNewsVerPOST"], [[NSUserDefaults standardUserDefaults] objectForKey:@"localnewsupdate"]];
谁能帮我理解这是什么()?和:在Objective-c中?谢谢!!