Stewart, Robert wrote:Stewart, Robert wrote:
Ireneusz Szpilewski wrote:
class rtti_base { virtual void _dummy() {} };
Once you have virtual functions, you need a virtual destructor. Hence the base class should define a virtual destructor and then there's no need for _dummy().
Every class deriving from rtti_base can be queried by means of RTTI, in particular rtti_base class and dynamic_cast can be used in similar way as IUnknown and QueryInterface() in COM Object Model
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The main purpose of this class is to set some standard name for that pointer type.
Why is a common, standardized or de facto standard name needed? The usual case is to create a base class for each context in which a common
Great idea! :-D base is desired.
Because that could be a C++ standard common class as Object in C# or IUnknown in COM. Let's call it object_t. ;-) Just not forced by language rules, but used at will if needed. Anyone could attach to it and have generic pointer to objects. As in my example above, I have a room where are cats and girls. I want to give milk to cats and kiss girls. There are two classes: class Cat { public: void GiveMilk(); }; class Girl { public: void Kiss(); }; they have really nothing in common, but objects of both classes are in my room. So I add to them something by which I can hold them all via pointers, and, in addition, query about their types. Let's suppose you have the same problem with different (or not) classes and have used also rtti_base to hold them all. Then we both win! You can insert your objects into my container, and if by accidence they derive from Cat or/and Girl, they will be pleased in my room. If I put my objects into your collection std::stack<rtti_base*> for example, they can also be pleased if you GiveMilk() to Cats and Kiss() Girls. :-) (By the way std::shared_ptr<rti_base*> would give us C++ equivalent of IUnknown interface with metods: QueryInterface(); AddRef(); Release(); ) Ireneusz Szpilewski