How Can I Determine an Object's Type at Runtime in C ?

Finding the Type of an Object in C

An object's type can be determined using dynamic_cast. This method dynamically casts a datum from one pointer or reference type to another, verifying the cast's validity at runtime.

Usage:

To cast to a pointer type:

TYPE* dynamic_cast<TYPE*>(object);

To cast to a reference type:

TYPE& dynamic_cast<TYPE&>(object);

Result:

• If the cast is successful and the object is of the desired type, the result is the pointer or reference to the object.
• If the cast is unsuccessful (object is not of the desired type), the result is NULL for a pointer cast and throws a bad_cast exception for a reference cast.

Runtime Type Information (RTTI)

Dynamic_cast relies on RTTI, which is only available for polymorphic classes (i.e., those with at least one virtual method). In practice, this is not a significant limitation, as most base classes have a virtual destructor for proper cleanup in derived classes.

Example:

Here is an example using dynamic_cast to check if an object is of type B:

class A {};
class B : public A {
public:
    void b_function() {}
};

void func(A& obj) {
    B* b_ptr = dynamic_cast<B*>(&obj);
    if (b_ptr != nullptr) {
        b_ptr->b_function(); // Object is of type B
    } else {
        std::cout << "Object is not of type B" << std::endl;
    }
}

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