1. Makoto Asai (SLAC) Geant4 Users Workshop @ CERN Nov. 13th, 2002
More on User Commands
Makoto Asai (SLAC)
Geant4 Users CERN
Nov. 13th, 2002

2. Contents User-defined command User-defined messenger
String stream object
G4ExceptionHandler
More on User Commands - M.Asai (SLAC) - Geant4 Users CERN (Nov/13/2002)

3. UI command and messenger
(G)UI
G4UImessenger
messenger
2. apply
1. register
4. invoke
3. do it
UImanager
command
Target class
parameter
More on User Commands - M.Asai (SLAC) - Geant4 Users CERN (Nov/13/2002)

4. User command
To define user commands, you need to make your own concrete messenger class implementation
class G4ParticleGun;
class G4UIcmdWithADoubleAndUnit;
#include "G4UImessenger.hh"
class G4ParticleGunMessenger: public G4UImessenger {
public:
G4ParticleGunMessenger(G4ParticleGun * fPtclGun);
~G4ParticleGunMessenger();
void SetNewValue(G4UIcommand * command,G4String newValues);
G4String GetCurrentValue(G4UIcommand * command);
private:
G4ParticleGun * fParticleGun;
G4UIcmdWithADoubleAndUnit * energyCmd; };
More on User Commands - M.Asai (SLAC) - Geant4 Users CERN (Nov/13/2002)

5. Messenger class Constructor
Instantiate command objects, set guidance, parameter information, etc., and register commands to UImanager.
Destructor
Delete commands (automatically unregistered).
SetNewValue method
Convert parameter string to values
Invoke appropriate method of the target class object
GetCurrentValue method
Get current values from the target class object
Convert them to string and return the string
More on User Commands - M.Asai (SLAC) - Geant4 Users CERN (Nov/13/2002)

6. Command classes G4UIcommand
Base class, Still usable for complicated command
G4UIdirectory
Definition of (sub-)directory
G4UIcmdWith3Vector, G4UIcmdWith3VectorAndUnit, G4UIcmdWithADouble, G4UIcmdWithADoubleAndUnit, G4UIcmdWithAString, G4UIcmdWithABool, G4UIcmdWithAnInteger, G4UIcmdWithoutParameter
Each class has its adequate conversion methods between a string and values.
Application state(s), for which a command is valid, can be set.
More on User Commands - M.Asai (SLAC) - Geant4 Users CERN (Nov/13/2002)

7. Parameter Each parameter must have its unique name (within a command)
If a parameter is set as “omittable”, default value must be given, or “current value as default” flag must be set.
Range(s) of parameter(s) can be given by C++ syntax.
E.g. “x>=0. && y>= 0. && x > y”
Candidate list is a string consists of candidates separated by spaces.
directionCmd = new G4UIcmdWith3Vector("/gun/direction",this);
directionCmd->Set_guidance("Set momentum direction.");
directionCmd
->Set_guidance("Direction needs not to be a unit vector.");
directionCmd->SetParameterName("Px","Py","Pz",true,true);
directionCmd->SetRange("Px != 0 || Py != 0 || Pz != 0");
See section 7.2 of User's Guide For Application Developers for more detail and full example code.
More on User Commands - M.Asai (SLAC) - Geant4 Users CERN (Nov/13/2002)

8. String stream objects
G4cout and G4cerr are objects of ostream and they have G4strstreambuf buffer objects.
Strings are sent to G4UIsession concrete class for handling appropriate to a (G)UI.
G4UIsession is the base class of all (G)UIs or interfaces to GUIs. This base class has methods ReceiveG4cout and ReceiveG4cerr to receive strings.
To connect Geant4 to an external framework, the user must implement an interface concrete class derived from G4UIsession, so that the external framework can receive G4cout/G4cerr strings.
More on User Commands - M.Asai (SLAC) - Geant4 Users CERN (Nov/13/2002)

9. G4ExceptionHandler
Geant4 provides G4VExceptionHandler base class, which is “notified” once G4Exception occurs.
Geant4 provides G4ExceptionHandler concrete class for the “default” behavior of core dump.
Once the user implements and instantiates his/her own concrete class, it automatically overwrites the default behavior.
We are planning to enrich error messages and also to provide more flexible severities of exceptions.
At least for exceptions which are most likely user oriented.
More on User Commands - M.Asai (SLAC) - Geant4 Users CERN (Nov/13/2002)