class Observer


Module akonadi
Namespace Akonadi::AgentBase
Class Observer
Inherits
The interface for reacting on monitored or replayed changes.

The Observer provides an interface to react on monitored or replayed changes.

Since the this base class does only tell the change recorder that the change has been processed, an AgentBase subclass which wants to actually process the change needs to subclass Observer and reimplement the methods it is interested in.

Such an agent specific Observer implementation can either be done stand-alone, i.e. as a separate object, or by inheriting both AgentBase and AgentBase.Observer.

The observer implementation then has registered with the agent, so it can forward the incoming changes to the observer.

In the multiple inheritance approach the init() method automatically registers itself as the observer.

Example for stand-alone observer:

class ExampleAgent : public AgentBase
{
public:
ExampleAgent( const QString &id );

~ExampleAgent();

private: AgentBase.Observer *mObserver; };

class ExampleObserver : public AgentBase.Observer { protected: void itemChanged( const Item &item ); };

ExampleAgent.ExampleAgent( const QString &id ) : AgentBase( id ), mObserver( 0 ) { mObserver = new ExampleObserver(); registerObserver( mObserver ); }

ExampleAgent.~ExampleAgent() { delete mObserver; }

void ExampleObserver.itemChanged( const Item &item ) { // do something with item kDebug() << "Item id=" << item.id();

// let base implementation tell the change recorder that we // have processed the change AgentBase.Observer.itemChanged( item ); }

Example for observer through multiple inheritance:

class ExampleAgent : public AgentBase, public AgentBase.Observer
{
public:
ExampleAgent( const QString &id );

protected: void itemChanged( const Item &item ); };

ExampleAgent.ExampleAgent( const QString &id ) : AgentBase( id ) { // no need to create or register observer since // we are the observer and registration happens automatically // in init() }

void ExampleAgent.itemChanged( const Item &item ) { // do something with item kDebug() << "Item id=" << item.id();

// let base implementation tell the change recorder that we // have processed the change AgentBase.Observer.itemChanged( item ); }

Author Kevin Krammer



methods