ami guru wrote:
Hello Brian,
I did not understand why down-casting is not possible. Super class
can be downcasted to a concrete class through dynamic cast,
isnt it?
This is true only if you create the concrete class first. If the Group
was not originally constructed as a Switch (meaning the
osg::Switch::Switch() constructor was called), you can't just force it
to be one.
This is one of the fundamental concepts of object-oriented programming.
If you don't understand this, I'd recommend grabbing a C++ book and
reading through it. You really need to understand this to be able to
program effectively.
To summarize, this works:
// Create Switch object
osg::Switch * sw = new osg::Switch();
// Assign to parent class pointer
osg::Group * grp = sw;
// Cast back to Switch pointer
osg::Switch * sw2 = dynamic_cast<osg::Switch *>(grp);
This doesn't work:
// Create a Group object
osg::Group * grp = new osg::Group();
// Try to cast to a Switch pointer (cast will fail and return NULL)
osg::Switch * sw2 = dynamic_cast<osg::Switch *>(grp);
--"J"
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