我有一段代码可以检测NSString是否为NULL、nil等。但是，它会崩溃。这是我的代码:NSArray*resultstwo=[databaseexecuteQuery:@"SELECT*FROMprocessesWHEREready='yes'LIMIT0,1"];for(NSDictionary*rowtwoinresultstwo){NSString*getCaption=[rowtwovalueForKey:@"caption"];if(getCaption==NULL){theCaption=@"Photouploaded...";}elseif(getCaption==
