choosing an object to create

[slitvinov]

Hi,

I think I cannot make I good design decision in the following
situation
I have a class Particle. And a derived class PolymerParticle

Now I would like to create an object to represent the interaction
between two particles. For different pairs it should be a different
kind of interaction.
for Particle - Particle --- Interaction
for Particle - PolymerParticle --- PolymerHydroInteraction
for PolymerParticle - PolymerParticle -- PolymerPolymerInteraction

PolymerHydroInteraction and PolymerPolymerInteraction are derived from
the Interaction class.

At some point I have two pointers Particle*. And my current solution is
to create a function
Interaction* CreateInteraction(Particle*, Particle*)
This function uses dynamic_cast to convert Particle pointers and then
creates and returns the correct type of interaction.

Is there a better way to do the same thing? Maybe I am missing
something about C++.

[Phlip]

slitvinov wrote:

At some point I have two pointers Particle*. And my current solution is
to create a function
Interaction* CreateInteraction(Particle*, Particle*)
This function uses dynamic_cast to convert Particle pointers and then
creates and returns the correct type of interaction.

Is there a better way to do the same thing? Maybe I am missing
something about C++.

You have discovered the "double-dispatch problem". Don't cast your way out
of it.

http://www.google.com/search?q=c%2B%2B+double+dispatch

--
Phlip
http://c2.com/cgi/wiki?ZeekLand <-- NOT a blog!!!

[slitvinov]

Phlip wrote:

You have discovered the "double-dispatch problem". Don't cast your way out
of it.

http://www.google.com/search?q=c%2B%2B+double+dispatch

Thank you. The link is very helpful. I am not a computer scientist and
did not know about design patterns. I see I have a lot to learn.