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<!DOCTYPE concept
  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
<concept id="GUID-6A2160F0-6062-4E77-ABA3-B829AF9689FA" xml:lang="en"><title>Contacts
database events</title><prolog><metadata><keywords/></metadata></prolog><conbody>
<p>A client application of the Contacts Server can be set to observe changes
in the contacts database. When a change in the database occurs, the application
gets an event. The event carries information about the type of the event,
the contact ID, and the connection ID.</p>
<codeblock id="GUID-F552F563-6AA7-4E55-9E0E-F131E2B2C91B" xml:space="preserve">struct TContactDbObserverEvent
    {
    TContactDbObserverEventType iType;
    TContactItemId iContactId;
    TUint iConnectionId;
    };
</codeblock>
<p>The following event types are defined in the <parmname>cntdbobs.h</parmname>:</p>
<codeblock id="GUID-9022E0A5-8CF3-469E-B1D4-2B2CC607F852" xml:space="preserve">enum TContactDbObserverEventType
    {
    EContactDbObserverEventNull,
    EContactDbObserverEventUnused,
    EContactDbObserverEventContactChanged,
    EContactDbObserverEventContactDeleted,
    EContactDbObserverEventContactAdded,
    EContactDbObserverEventUnknownChanges,
    EContactDbObserverEventRecover,
    EContactDbObserverEventRollback,
    EContactDbObserverEventTablesClosed,
    EContactDbObserverEventTablesOpened,
    EContactDbObserverEventTemplateChanged,
    EContactDbObserverEventTemplateDeleted,
    EContactDbObserverEventTemplateAdded,
    EContactDbObserverEventCurrentItemDeleted,
    EContactDbObserverEventCurrentItemChanged,
    EContactDbObserverEventOwnCardChanged,
    EContactDbObserverEventPreferredTemplateChanged,
    EContactDbObserverEventOwnCardDeleted,
    EContactDbObserverEventGroupAdded,
    EContactDbObserverEventGroupChanged,
    EContactDbObserverEventGroupDeleted,
    EContactDbObserverEventCurrentDatabaseChanged,
    EContactDbObserverEventSpeedDialsChanged
    EContactDbObserverEventSortOrderChanged,
    EContactDbObserverEventBackupBeginning,
    EContactDbObserverEventRestoreBeginning,
    EContactDbObserverEventBackupRestoreCompleted,
    EContactDbObserverEventRestoreBadDatabase,
    };
</codeblock>
<p>To receive events on contact database changes, the application must
derive <xref href="GUID-4928B1DE-9800-3887-B456-2DDFE810AFD9.dita"><apiname>MContactDbObserver</apiname></xref> base class and implement <xref href="GUID-4928B1DE-9800-3887-B456-2DDFE810AFD9.dita#GUID-4928B1DE-9800-3887-B456-2DDFE810AFD9/GUID-DECA9730-0504-3D4F-85D4-AFAC70B46580"><apiname>MContactDbObserver::HandleDatabaseEventL()</apiname></xref> virtual
function. The function is called by the system when a contact database event
occurs.</p>
<codeblock id="GUID-EEB33DFB-0009-4CE5-BC96-41B65519F8D1" xml:space="preserve">class CMyContactObserver : public CBase, public MContactDbObserver
    {
     public:
         // any public data and functions
         CMyContactObserver ();
         // override the virtual function from the base class
         virtual void HandleDatabaseEventL( TContactDbObserverEvent aEvent );
         };
     // handling contact database events
     void CMyContactObserver::HandleDatabaseEventL( TContactDbObserverEvent aEvent )
         {
         // Event handling code
         }
</codeblock>
<p>In addition, the application must create the <xref href="GUID-140725B3-8D52-3D2B-9E72-CAF76962B95A.dita"><apiname>CContactChangeNotifier</apiname></xref> object
to register itself to receive events.</p>
<codeblock id="GUID-95A974D8-3D88-4E64-8A33-AF2366C34791" xml:space="preserve">CContactDatabase* contactDb = CContactDatabase::OpenL();
//iContactDbObserver is a CMyContactObserver pointer
CContactChangeNotifier* notifier = CContactChangeNotifier::NewL( *contactDb, iContactDbObserver );
</codeblock>
</conbody></concept>