Use of Ref and Persistent Objects

Question

Hi,
I am using OTT and I have created a sub class for the OTT generated class
i.e.,
class A:public PObject//OTT generated
class B:public A//created by me
for Class B I need to write a static function queryKey() which will return a pointer to persistent object of class B,
i.e.,
B* B::queryKey(Number c,Number d);
I have implemented it something like this...
B* B::queryKey(      OCCI_STD_NAMESPACE::string c,
                    oracle::occi::Number d,
                    oracle::occi::Number e)
     Statement *stmt=NULL;
     ResultSet *rset=NULL;
     CCPDKey *handle=0;
     try
          string query="SELECT REF(a) FROM ";
          query=query+tableName+ (" a WHERE C=:1 AND D=:2 AND E=:3 ");
          stmt=conn->createStatement(query);
          stmt->setString(1,c);
          stmt->setNumber(2,d);
          stmt->setNumber(3,e);
          rset=stmt->executeQuery();
          if(rset->next())
               Ref < B > r1(rset->getRef(1));
               handle=r1.ptr();
     catch(...)
          stmt->closeResultSet (rset);
     conn->terminateStatement (stmt);
          throw;
     stmt->closeResultSet (rset);
conn->terminateStatement (stmt);
     return handle;
Is this the correct way of doing it,
Will the persistent object pointed by handle get destroyed as the scope of Ref i.e.,r1 ends..?
If so, what is the correct way of doing it..?
I need this method to return a B*.
If the way I have used is correct,Do I need to delete the variable handle once I am done using it..?I saw in "Using OCCI: Best Practices" that the persistent object should not be deleted unless you are doing rollback.
I am new to OCCI and i am confused
Please help
Ajey

Answer 1

In the function B::queryKey(), the Ref<B> variable will go out of scope at the end of the if {} statement and the Ref will be unpinned. So, the "handle" object pointer variable will be pointing to an object that could be freed anytime by the garbage collector.
Can you change your design to return a Ref<B> from B::queryKey()? If you want to return the object pointer directly then you will have to manage pining/unpining of the object. With Refs, the pining/unpining is transparently managed by OCCI and with the "->" operator you can write code which is the same as with the object pointer.
Thanks,
Shankar