Rtti

[Sayan Mukherjee]

Hi,

Suppose the relationship of two classes viz. Base and Derived
are such that:

class Base
{
};
 
class Derived : public Base
{
}; 

The class Base contains at least one virtual function.

We can do the following:

Base *pBase = new Base();
Derived *pDerived = new Derived();

pBase = pDerived; 

This demonstrates polymorphism in C++.

My question is:

Is this behaviour included under RTTI?

Though this does not need to use dynamic_cast, type_id and
type_info, this also is a form of identifying type at runtime.
The limitation is: it is 'up the inheritance chain' only instead of
anywhere in the class hierarchy.

Thanks is advance.


With best regards,
Sayan Mukherjee
[Email: sayan2405@vsnl.net]

[treuss]

Originally posted by Sayan Mukherjee

Base *pBase = new Base();
Derived *pDerived = new Derived();

pBase = pDerived;

Is this behaviour included under RTTI?

There is no RTTI involved here, just static type checking.
The fact that an object of Derived is-an object of Base is defined statically, it can be checked at compile time, not at run time. RTTI is only needed if you have to evaluate dynamic type information. Example:

Base * pBase = 0;
if ( ... )
  pBase = new Base();
else
  pBase = new Derived();

// We cannot determine at compile time if the following will succeed
Derived *pDerived = dynamic_cast<Derived*>(pBase);