Using C++, on unix through g++ I need some info on how to use the typeid() function. Any website indications would be great. specifically, i have class b and c, which are both derived from class a. in my main program, I use an iterator for a vector of a* to traipse the list, and i believe if (typeid(*iter) == typeid(b)) {...} else {other stuff) should pick out the objects of type b. The iterator is pointing to the right objects, (checked with a display() funct, I have included the typeinfo lib. always with b objects, other stuff is done instead of ...

I think what you are doing is correct. Maybe there is a compiler flag you need to set to turn on RTTI. I know there is such a flag in VC.

HTH

Doug Sutherland

Does''nt seem to need one from what i can find - thanks anyway

I''m not sure your still looking for help on this but.

I''m not sure about the typeid, but in the past I''ve used dynamic_cast to achieve the same thing. Internally I guess dynamic_cast use the typeid information.

To use dynamic casts you need to do something like

class CGameObject;class CPlayer : public CGameObject;vector::iterator iter;iterating through a vector of CGameObject pointers you might useCPlayer* player = dynamic_cast(*iter);if ( player != NULL ){  //Process player specific code} 

Basically the dynamic cast returns a valid pointer if CGameObject* is actually a CPlayer ( CPlayer derived class ).

To use dynamic casts and ( I guess ) typeid the classes involved must have at least one virtual function. And as Doug said you''ll also need to set a compiler option enabling rtti.

Under djgpp (might be the same as unix g++) use
-frtti
Under VC++
/GR


Tom.

TheHermit, I think that you should avoid to use the typeid() function for doing such a branching while you are swepping thru'' a list of items.

(in general, I think the typeid() function should always be avoided)

Just add a virtual "shouldIPickIt()" boolean class observed in class A and redefine it in class B and C so that is returns "true" if pointing to an instance of class B.

For example:

class A { // ...public: virtual bool shouldIPickIt() = 0; // ...}class B { // ...public: bool shouldIPickIt() { return(true) }; // ...}class B { // ...public: bool shouldIPickIt() { return(false) }; // ...}

Hope it (still) helps.



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Weeelll, seems i found a satisfactory answer to my problem...

Someone suggested use (typeid(**iter) == typeid(b)), which, well, works.

Bugger of a thing is, have seen, and confirmed my initial way working in a different program, same system, compiler version, libraries, etc.

Only difference really is - that prog is all in one file, headers, classes, program, everything. Mine is in seperate files: a.h, b.h, a.cpp, b.cpp, main.h, main.cpp. Everything else works the initial way....


AAAAAAHHHHHHH!!!!!!!!

(oh well...)