Following a link to another table and finding a field by Id and by name: Tutorial

This tutorial shows you how to follow a link to a Symbian platform defined table. The tutorial also shows two methods to get the value of a field.

Steps

1. Make sure that you have created a session.

2. Create the IAP record object in the tool or application process and prime it for the search for the service type "DialOutISP".

   Symbian platform defines the CCDIAPRecord class to represent a IAP record. The class is a schema for the record. The class defines the fields and links that make a IAP record. Symbian platform defines unique numeric Id s for Symbian platform defined tables. The symbol [[[ERROR: [NOKX000E] Unable to find definition for key reference 'CommsDat']]]KCDTIdIAPRecord defines the value of this Id for the IAP table. The Id allows the CommsDat API to retrieve the table from the Comms Database efficiently.

   ...
   // Create a single IAP record in memory and prime it with the type of service
   // that you want to find. In this case, the type of service is "DialOutISP".
   // This code fragment assumes that a session with the Comms Database has been created.
   // "iDb" is a pointer to a CMDBSession object
   
   _LIT(KISPType, "DialOutISP");
   TUint32 bearerSpeed;
   
   
   // Use the factory function CCDRecordBase::RecordFactoryL() to create the IAP record obejct. 
   //
   // Note:
   // 1. the template parameter CCDIAPRecord defines 
   //    the "IAP" record type.
   // 2. the unique numeric Id KCDTIdIAPRecord is passed as a parameter
   //    to the constructor.
   
   CCDIAPRecord* ptrSingleIAPRecord = static_cast<CCDIAPRecord*>(CCDRecordBase::RecordFactoryL(KCDTIdIAPRecord)); 
   
   
   // The storage for string or binary fields must be allocated
   // explicitly if set or reset by the application. Storage required for
   // storing data  retrieved from the database is handled by the implementation of the CommsDat API.
   //
   // Set the service type.
   ptrSingleIAPRecord->iServiceType.SetMaxLengthL(KISPType().Length());
   ptrSingleIAPRecord->iServiceType = KISPType; 
   
   
   // Note that you can replace the above two function calls with the 
   // single function call:
   //
   // ptrSingleIAPRecord->iServiceType.SetL(KISPType); 
   ...

3. Search for the first IAP record that has "DialOutISP" as the service type. If the record is found, load the associated service table record.

   ...
   if(ptrSingleIAPRecord->FindL(*iDb))
       { 
       // An IAP record with "DialOutISP" as the service type has
       // been found and loaded into memory. 
        
       // Load the service table record associated with this IAP.
       ptrSingleIAPRecord->iService.LoadL(*iDb);
       ...

4. 1. CASE 1 : Access the service record when you know the service type. This is the most effiecient method.

          ...
          CCDDialOutISPRecord* ptrIspRecord = static_cast<CCDDialOutISPRecord*>(ptrSingleIAPRecord->iService.iLinkedRecord);
          bearerSpeed = ptrIspRecord->iBearerSpeed;
          ...

   2. CASE 2: Access the service record when you do not know the service type. This is also the more general case and is slower than case 1.

      You can find a field by its Id, or you can find a field by its name. To find a field by its name is not recommended, because this operation is slow.

          ...
          // Use the base class "CCDServiceRecordBase" instead of the more specific
          // class "CCDDialOutISPRecord" [or any other specific class derived from "CCDServiceRecordBase"].
          CCDServiceRecordBase* ptrServiceRecord = static_cast<CCDServiceRecordBase*>(ptrSingleIAPRecord->iService.iLinkedRecord);
          CMDBField<TUint32>* field; 
          ...
      
          // Find a field by its Id
      
          field = (CMDBField<TUint32>*)ptrServiceRecord->GetFieldByIdL(KCDTIdBearerSpeed);
          bearerSpeed = *field;
          ...
      
         // Find a field by its name. Symbian platform defines KCDTypeNameBearerSpeed to represent 
         // the name of the field.
      
          TPtrC16 BearerName(KCDTypeNameBearerSpeed);
          TInt valueType; 
          field = (CMDBField<TUint32>*)ptrServiceRecord->GetFieldByNameL(BearerName,valueType);
          bearerSpeed = *field;
          ...
          

5. Clean up.

       ...
       //
       // This also deletes "ptrSingleIAPRecord->iService.iLinkedRecord"     
       //
       delete ptrSingleIAPRecord;
       ...        
       }
   }