Wt

I just did the same thing and I don't get that error.

 52 user_ptr get_logged_in_user(void)                                                                
 53 {                                                                                                                 
 54     if (!login.loggedIn())                                                                                        
 55         return nullptr;                                                                                           
 56     Wt::Dbo::Transaction t{session};                                                                              
 57     auto auth_info{users.find(login.user())};                                                                     
 58     auto ret{auth_info->user()};                                                                                  
 59     ret.remove();                                                                                                 
 61     return ret;                                                                                                   
 62 }     

Assuming you're using the example I think you are, this code should be roughly equivalent. It seems like something else is going on...can you show more code maybe? I know a minimum working example is a lot to ask in this case! But if your code is on github...

Rajveer, can you paste the function definition that this is being run in?

For example, in the post above, the function definition is:

user_ptr get_logged_in_user(void)

What is yours?

Hey Mark, lm

Thank you for responding. The above example now works, what I realized is I was loosing scope of the transaction i.e. from the point where I start my dbo transaction and the line where I actually call the .remove() method, some nesting already took place and "maybe" that was what that caused this error. It works now since I changed the control flow.

My function definition is a simple container widget that is populating some table from back-end(MySQL) and on clicking on certain button the specific user gets deleted(vanilla CRUD functionality).

Wt::WContainerWidget *UserScreen::populateListModelsTable()

Although I have another few things that I can use some clarity on-

1. How can I access auto generated object field "id" when my objects are stored in MySQL. On calling a usual object->id or object.id an error is thrown saying the stated class does not have a member variable called "id"(where object is a Wt::Dbo::ptr).

2. For a scenario where user object can have multiple filling model object on trying to iterate over the filling model objects via the following-

for (dbo::collection< dbo::ptr<FillingModel> >::const_iterator i =
user->fillingModel.begin(); i != user->fillingModel.end(); ++i) {
const FillingModel& fm = **i;}

I can access specific attribute values for each filling model via fm.attribute_name, but I can not access fm.id (same error as mentioned in 1. above). Also I can not use fm.remove() on this either.

As a workaround I am initializing another dbo::ptr and then call .remove() method on this. It works but I am not happy with this solution as I am not able to understand what is going wrong here.

dbo::ptr<FillingModel> fmodel = session_.find<FillingModel>().where("shortModelDesc = ?").bind(fm.shortModelDesc);

Thanks again for participating in this discussion.

RV

Ok, good! I realized my question made no sense... so good, glad you found that issue;

1. How can I access auto generated object field "id"

(psudo code)

node: resultValue() returns 1 item, and throws on multiple

   auto myItem = session()-> find<MyClass>().where("id = ?").bind( myId ).resultValue();
   std::cout << myItem.id() << std::endl;

...or something to that effect.

2. For a scenario where user object can have multiple filling model object

note: resultList() returns an item collection

   auto myItems = session()-> find<MyClass>().where("city = ?").bind( mycity ).resultList();
   for( auto item : myItems )
   {
     cout << item.id() << " " << item-> someField() << endl;
   }

...or something to that effect

Rajveer Shringi wrote:

1. How can I access auto generated object field "id" when my objects are stored in MySQL. On calling a usual object->id or object.id an error is thrown saying the stated class does not have a member variable called "id"(where object is a Wt::Dbo::ptr).

Make sure your class extends Wt::Dbo::Dbo. This base class will provide some convenience: an id(), ready access to the Wt::Dbo::Session, and a Wt::Dbo::ptr to this. https://www.webtoolkit.eu/wt/doc/reference/html/classWt_1_1Dbo_1_1Dbo.html

lm at wrote:

Make sure your class extends Wt::Dbo::Dbo. This base class will provide some convenience: an id(), ready access to the Wt::Dbo::Session, and a Wt::Dbo::ptr to this. https://www.webtoolkit.eu/wt/doc/reference/html/classWt_1_1Dbo_1_1Dbo.html

Thanks, this works. I was not extending my object classes from this base class.

Oh yeah, there is a huge caveat (I think it's still applicable): delete your copy constructor (or at least don't use it). I remember running into some terribly confusing bugs that Mr. Koen helped me work through and the answer was: Wt::Dbo::Dbo doesn't support copy (but doesn't delete its copy constructor either).

That was a long time ago, and I'm hopeful the issue has been more satisfactorily dispatched in the meantime, but I haven't bothered testing a recent version.