Loading a Symbian platform Defined Table, Changing a Field, Write Changed Record: Tutorial

This tutorial shows you how to load a Symbian platform defined table from the Comms Database, change a field, and write the changed record to the database.

1. Make sure that you have created a session.
2. Create the table object in the tool or application process. You create a CMDBRecordSet <T> object and specify CCDIAPRecord as the template parameter. 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 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. To work with other Symbian platform defined tables, use the correct class name and the correct unique numeric Id values. The Reference section contains a list of all Symbian platform defined tables.

   ...
   
   // This code fragment assumes that a session with the Comms Database has been created.
   // iDb is a pointer to a CMDBSession object
   ...
   
   // Use the standard "new (ELeave)" construction to create the object to 
   // represent the table. 
   //
   // 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.
   CMDBRecordSet<CCDIAPRecord>* iapRecordSet = 
      new (ELeave) CMDBRecordSet<CCDIAPRecord>(KCDTIdIAPRecord);
   ...
                

3. Create a record that contains the type of Service Typefield needed. To search for a record the tool or application creates a record in memory. The fields in the record are set to the specific values on which the search is to match. In this tutorial this record is called the "search record". The record is appended to the set of records in the table object. At this point, the search record is the only record in the table, because the Comms Database has not yet been accessed. In this tutorial, the Service Type field in the search record is set to DialOutISP.

   ...
   // Searching for all IAP records that support the DialOutISP service.
   _LIT(KServiceType, "DialOutISP");
   
       
   // Create the "search record". You use the unique numeric Id KCDTIdIAPRecord 
   // to identify the type record to the factory function.
   CCDIAPRecord* ptrPrimingRecord = static_cast<CCDIAPRecord *>
       (CCDRecordBase::RecordFactoryL(KCDTIdIAPRecord));
   
   
   // Prime the Service    Types field with the string "DialOutISP"
   ptrPrimingRecord->iServiceType.SetMaxLengthL(KServiceType().Length());
   ptrPrimingRecord->iServiceType = KServiceType; 
   
   
   // Append the search record to the table in memory. Remember that the table only 
   // contains this record. The Comms Database has not yet been accessed.
   iapRecordSet->iRecords.AppendL(ptrPrimingRecord);
   
   
   // Set the record pointer to NULL, because ownership of the "search record" has
   // been passed to the table object.
   ptrPrimingRecord = NULL; 
   ...

4. Perform the search. Use the FindL() function to search the table in the Comms Database. The function is called on the class that defines the table. The function is implemented in the base class MMetaDatabase. You pass a reference to the session object into the FindL() function.

   ...
   // Perform the search. 
   if(iapRecordSet->FindL(*iDb))
       {
       // At least one record found. 
       // Find the number of records found.   
       TInt iapRecordsFound = iapRecordSet->iRecords.Count();
   
       // Change the Network Weighting field in the last record.
       CCDIAPRecord* iapRecord = 
           static_cast<CCDIAPRecord*>( iapRecordSet->iRecords [iapRecordsFound-1]);
       iapRecord->iNetworkWeighting = 1;
   
       // Update the changed record in the Comms Database
       
       // EITHER
       // Check through all records and submit all changes
       // made by the tool or application.
       iapRecordSet->ModifyL(*iDb);
   
       // OR 
       // Explicitly submit this record only
       iapRecord ->ModifyL(*iDb); 
       ...
       }
   else 
       {
       // No matching records found.
       // Note that iRecords[0] still contains the "search record". The "search record"
       // only contains the priming values.
       // It is important to check the return code from the call to ModifyL()
       }           
   ...