Event/message/notification class. More...

#include <mitkMessage.h>

Inheritance diagram for mitk::Message< A >:

Collaboration diagram for mitk::Message< A >:

Public Types
typedef MessageBase< MessageAbstractDelegate< A > >	Super

typedef Super::ListenerList	ListenerList

Public Types inherited from mitk::MessageBase< MessageAbstractDelegate< A > >
typedef std::vector< MessageAbstractDelegate< A > * >	ListenerList

Public Member Functions
void	Send ()

void	operator() ()

Public Member Functions inherited from mitk::MessageBase< MessageAbstractDelegate< A > >
virtual	~MessageBase ()

	MessageBase ()

	MessageBase (const MessageBase &o)

MessageBase &	operator= (const MessageBase &o)

void	AddListener (const MessageAbstractDelegate< A > &delegate) const

void	operator+= (const MessageAbstractDelegate< A > &delegate) const

void	RemoveListener (const MessageAbstractDelegate< A > &delegate) const

void	operator-= (const MessageAbstractDelegate< A > &delegate) const

const ListenerList &	GetListeners () const

bool	HasListeners () const

bool	IsEmpty () const

Additional Inherited Members
Protected Attributes inherited from mitk::MessageBase< MessageAbstractDelegate< A > >
ListenerList	m_Listeners
	List of listeners. More...

itk::SimpleFastMutexLock	m_Mutex

Detailed Description

template<typename A = void>
class mitk::Message< A >

Event/message/notification class.

See also: mitk::BinaryThresholdTool; QmitkBinaryThresholdToolGUI

This totally ITK, Qt, VTK, whatever toolkit independent class allows one class to send out messages and another class to receive these message. This class is templated over the return type (A) of the callback functions. There are variations of this class (Message1, Message2, etc.) for sending one, two or more parameters along with the messages.

This is an implementation of the Observer pattern.

There is no guarantee about the order of which observer is notified first. At the moment the observers which register first will be notified first.
Notifications are synchronous, by direct method calls. There is no support for asynchronous messages.

To conveniently add methods for registering/unregistering observers to Message variables of your class, you can use the mitkNewMessageMacro macros.

Here is an example how to use the macros and templates:

// An object to be send around
class Law
{
  private:
    std::string m_Description;
  public:
    Law(const std::string law) : m_Description(law)
    { }
    std::string GetDescription() const
    {
      return m_Description;
    }
};
// The NewtonMachine will issue specific events
class NewtonMachine
{
  mitkNewMessageMacro(AnalysisStarted);
  mitkNewMessage1Macro(AnalysisStopped, bool);
  mitkNewMessage1Macro(LawDiscovered, const Law&);
  public:
    void StartAnalysis()
    {
      // send the "started" signal
      m_AnalysisStartedMessage();
      // we found a new law of nature by creating one :-)
      Law massLaw("F=ma");
      m_LawDiscoveredMessage(massLaw);
    }
    void StopAnalysis()
    {
      // send the "stop" message with false, indicating
      // that no error occured
      m_AnalysisStoppedMessage(false);
    }
};
class Observer
{
  private:
    NewtonMachine* m_Machine;
  public:
    Observer(NewtonMachine* machine) : m_Machine(machine)
    {
      // Add "observers", i.e. function pointers to the machine
      m_Machine->AddAnalysisStartedListener(
        ::mitk::MessageDelegate<Observer>(this, &Observer::MachineStarted));
      m_Machine->AddAnalysisStoppedListener(
        ::mitk::MessageDelegate1<Observer, bool>(this, &Observer::MachineStopped));
      m_Machine->AddLawDiscoveredListener(
        ::mitk::MessageDelegate1<Observer, const Law&>(this, &Observer::LawDiscovered));
     }
    ~Observer()
    {
      // Always remove your observers when finished
      m_Machine->RemoveAnalysisStartedListener(
        ::mitk::MessagDelegate<Observer>(this, &Observer::MachineStarted));
      m_Machine->RemoveAnalysisStoppedListener(
        ::mitk::MessageDelegate1<Observer, bool>(this, &Observer::MachineStopped));
      m_Machine->RemoveLawDiscoveredListener(
        ::mitk::MessageDelegate1<Observer, const Law&>(this, &Observer::LawDiscovered));
     }
     void MachineStarted()
     {
       std::cout << "Observed machine has started" << std::endl;
     }
     void MachineStopped(bool error)
     {
       std::cout << "Observed machine stopped " << (error ? "with an error" : "") << std::endl;
     }
     void LawDiscovered(const Law& law)
     {
       std::cout << "New law of nature discovered: " << law.GetDescription() << std::endl;
     }
 };
 NewtonMachine newtonMachine;
 Observer observer(&newtonMachine);
 // This will send two events to registered observers
 newtonMachine.StartAnalysis();
 // This will send one event to registered observers
 newtonMachine.StopAnalysis();