observer::IObserver< T > Class Template Reference

#include <observer.h>

Inheritance diagram for observer::IObserver< T >:

Public Types
typedef int	priority_t
Public Member Functions
	IObserver ()
virtual void	notify (boost::shared_ptr< T > newValue, boost::shared_ptr< const IChangeContext< T > > context) const =0 throw ()
virtual priority_t	getPriority () const =0 throw ()
bool	setActive (bool active)
bool	isActive () const
virtual	~IObserver () throw ()
Private Attributes
bool	active

Detailed Description

template<typename T>
class observer::IObserver< T >

Observer interface (pure abstract class).

Observer is mechanism how to be informed that somethig has changed. Implementator of this interface produces handler for this change event.
This should be used in following way:

value keeper which wants to enable observers has to implement ObserverHandler interface which enables to register and unregister observers. It guaranties it calls notify on each registered observer after change was registered.
implementator of class is responsible for notify method implementation which handles situation.
observer must be registered on target value keeper.

Interface is template to enable different value types to be used (type parameter stands for value type to be managed - informed about change). This enables only one type to be handled by one implementator (with all subtypes).
Value change handling is done in notify method (see for more details). This method is called after value has been changed.
Each observer implementation has its priority which is used be value keeper to determine order in which to notify obsevers, if there is more then one.
Observer can be in active/inactive state depending on the active flag value. See setActive, isActive methods.
Exception NOTE: No method throws an exception.

Member Typedef Documentation

template<typename T>

typedef int observer::IObserver< T >::priority_t

Type for priority.

Constructor & Destructor Documentation

template<typename T>

observer::IObserver< T >::IObserver ( ) [inline]

Default constructor.

template<typename T>

virtual observer::IObserver< T >::~IObserver ( ) throw () [inline, virtual]

Virtual destructor.

Member Function Documentation

template<typename T>

virtual priority_t observer::IObserver< T >::getPriority ( ) const throw () [pure virtual]

Returns priority of obsever.

Lower number means higher priority.

Returns:: Observer priority value.

Implemented in pdfobjects::CContentStream::CStreamObserver, pdfobjects::CContentStream::OperandObserver, pdfobjects::CPageAnnots::PropWatchDog, pdfobjects::CPageAnnots::ArrayWatchDog, pdfobjects::CPageContents::ContentsWatchDog, pdfobjects::CPdf::PageTreeRootObserver, pdfobjects::CPdf::PageTreeNodeObserver, pdfobjects::CPdf::PageTreeKidsObserver, pdfobjects::utils::ProgressObserver, gui::TreeItemGenericObserver< ObservedItem >, gui::TreeItemGenericObserver< pdfobjects::IProperty >, gui::TreeItemGenericObserver< pdfobjects::CContentStream >, and gui::TreeItemGenericObserver< pdfobjects::CPage >.

template<typename T>

bool observer::IObserver< T >::isActive ( ) const [inline]

Returns current value of the active flag.

Returns:: true if observer can be notified, false otherwise.

template<typename T>

virtual void observer::IObserver< T >::notify	(	boost::shared_ptr< T >	newValue,
		boost::shared_ptr< const IChangeContext< T > >	context
	)			const throw () `[pure virtual]`

Notify method.

Parameters:

	newValue	New value of changed value or its part.
	context	Value change context.

Each time value keeper, which implements ObserverHandler, changes value (or its part), all registered observers are notified about that by this method calling.
newValue stands for new value or its part (if value is complex).
contex contains additional information about change. It depends on value keeper which information is provided (if any). It may be NULL (value stored in shared_ptr may be NULL - more precisely - use contex.get()==NULL condition for checking) which means that no information is provided. Method implementator should check context type (using getType() method). Accoring this type cast to correct IChangeContext subclass and use information.

Example:
Lets say that T is IProperty. If observer is registered on simple type, newValue contains new value of this simple one. If it is registered on complex type, it contains changed value (item) inside this complex type (value keeper part is changed).

Implemented in gui::TreeItemGenericObserver< ObservedItem >.

template<typename T>

bool observer::IObserver< T >::setActive ( bool active ) [inline]

Sets active flag value.

Parameters:

active

Flag value to be set.