Observer interface for MdE database queries.

Example of doing a query to metadata database:

A class needs to implement MMdEQueryObserver interface if it is going to do a query to MdE database.

class CMdEQueryExample : public MMdEQueryObserver { void HandleQueryNewResults(CMdEQuery& aQuery, TInt aFirstNewItemIndex, TInt aNewItemCount); void HandleQueryCompleted(CMdEQuery& aQuery, TInt aError); ... CMdESession* iMdeSession; // session to MdE, created before trying to do the query CMdEQuery* iQuery; };

void CMdEQueryExample::DoQuery() { CMdENamespaceDef& defNS = iMdeSession->GetDefaultNamespaceDefL();

// In this function we create a query with following conditions: // Right object in relation must be a location object. // Left object in relation must have id 6.

// First create an object query. We want to find location objects so let's give that // as a condition to the query. CMdEObjectDef& rightObjDef = defNS.GetObjectDefL( MdeConstants::Location::KLocationObject ); iQuery = iMdeSession->NewObjectQueryL( defNS, rightObjDef, this );

// Result mode EQueryResultModeItem means we want the query to return items. // Other options are: EQueryResultModeId, EQueryResultModeCount, // EQueryResultModeDistinctValues and EQueryResultModeObjectWithFreetexts. iQuery->SetResultMode( EQueryResultModeItem );

// ELogicConditionOperatorAnd means we want all conditions to be true. iQuery->Conditions().SetOperator( ELogicConditionOperatorAnd );

// Add a relation condition to the query. The location object is the right side object of // the relation. CMdERelationCondition& filterCond = iQuery->Conditions(). AddRelationConditionL( ERelationConditionSideRight );

// The object on the left side of the relation must have ID 6. filterCond.LeftL().AddObjectConditionL( 6 );

iQuery->FindL( 10, 1 ); // Start the query! The first parameter is maximum number of result items. // The second parameter is number of results per observer // notification. This query returns maximum of 10 location items // and gives a notification (HandleQueryNewResults) for each. }

void CMdEQueryExample::HandleQueryCompleted( CMdEQuery& aQuery, TInt aError ) { // query is completed if( aQuery.Count() > 0 && aError == KErrNone ) { // some items were found! } }

void CMdEQueryExample::HandleQueryNewResults(CMdEQuery& aQuery, TInt aFirstNewItemIndex, TInt aNewItemCount) { // query is not yet completed but new results were found }

CMdEQuery::FindL