[Insight-developers] GetMacro vs GetConstMacro

[Miller, James V (CRD)]

I have been struggling with this as well.  I think the solution is probably to have more macros.  I
think of it as a matrix of options:

1) Do I want to return a copy or a reference to a item?
2) Do I want the user to be able to modify the item returned, is item const?
3) Do I want the user to be able call the method on a const object?

There is a forth option of calling on a const object AND allowing the user to modify the return value
but that case should be avoided.  So to me it seems as though there should be 3 macros.


-----Original Message-----
From: Luis Ibanez [mailto:ibanez@cs.unc.edu]
Sent: Tuesday, February 20, 2001 12:09 PM
To: insight-developers@public.kitware.com
Subject: [Insight-developers] GetMacro vs GetConstMacro


Hi,

itkGetMacro( name, type ) generates:

virtual   type  GetName(void ) {
   return m_Name;
}


itkGetConstMacro(name, type ) generates:

virtual const type GetName( void ) const {
  return m_Name;
}


The second is maybe the one that we should
use most of the time, because in general a Get()
operation doesn't modify the object.

But, some compiles complain when they find

const int GetName()...   because 'const'
is meaninless when passing by value.

-----

Most of the time GetConstMacro is used to get
access to a member variable in the class. Could
we use a pass by reference instead of passing
by value in GetConstMacro ?

like:

itkGetConstMacro( name, type )

virtual const type & GetName(void ) const {
   return m_Name;
}


----

This is important for enforcing constness in other places.
for example, now it is not possible to call :

GetProgress()
GetNumberOfThreads();
GetNumberOfRequiredInputs();
GetNumberOfRequiredOutput();

on a const itkProcessObject  (that means: in any const filter)

-----------


Thanks


Luis

_______________________________________________
Insight-developers mailing list
Insight-developers@public.kitware.com
http://public.kitware.com/mailman/listinfo/insight-developers