Fwd: Visitor ...

[Angus Leeming]

Look what I dug out of my mailbox. Did anything ever come of this?

Angus

----------  Forwarded Message  ----------

Subject: Visitor ...
Date: Fri, 14 Dec 2001 05:15:44 +0000
From: John Levon <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]

here's a working example of what Ben had designed (did this so I
could work out what he was saying :)

Dunno about others, but I prefer the name of visitInset to stay
the same no matter what ...

the two problems ben has been trying to fix with this (accompanied
by stupid questions from myself) are :

1) each inset has to be listed in InsetVisitor

2) each inset HAS to have an acceptVisitor() method

I still think it's worth it, even better if anyone can solve either
of these problems ...

regards
john

#include <iostream>

class Inset;
class InsetERT;

class InsetVisitor {
// blah blah
public:
        // need every possible inset listed here
        // for dynamic dispatch based on inset type,
        // to be robust against future visitor classes
        virtual void visitInset(Inset &)  {};
        virtual void visitInset(InsetERT &) {};
};

class Inset {
// blah blah
public:
        virtual void acceptVisitor(InsetVisitor & iv) {
                iv.visitInset(*this);
        }
};

class InsetERT : public Inset {
// blah blah
private:
        // need this here to get the right type for visitInset
        virtual void acceptVisitor(InsetVisitor & iv) {
                iv.visitInset(*this);
        }
};

class SpellCheckInsetVisitor : public InsetVisitor {
public:
        virtual void visitInset(Inset &) {
        // do default spellcheck
                std::cout << "default spellcheck" << std::endl;
        }
        virtual void visitInset(InsetERT &) {
        // don't do any spellcheck !!
                std::cout << "ert no spellcheck" << std::endl;
        }

        // this is the top-level code
        void doSpellcheck() {
                //for_each(bv.inset_iterator_begin(), bv.inset_iterator_end(),
 acceptVisitor(this)); Inset * ie = new InsetERT;
                ie->acceptVisitor(*this);
        }
};

int main() {
        SpellCheckInsetVisitor v;
        v.doSpellcheck();
}