=====dynamic_cast=====
Syntax:

<code cpp>
    T& dynamic_cast<T&> (object);
    T* dynamic_cast<T*> (object);
</code>

The ''dynamic_cast'' keyword casts ''object'' from one pointer or reference type to another, performing a runtime check to ensure the validity of the cast. 

If you attempt to cast to a pointer type, and that type is not an actual type of the argument object, then the result of the cast will be **NULL**.

If you attempt to cast to a reference type, and that type is not an actual type of the argument object, then the cast will throw a [[/support/rtti/bad_cast|std::bad_cast]] exception.

<code cpp>
  struct A {
    virtual void f() { }
  };
  struct B : public A { };
  struct C { };

  void f () {
    A a;
    B b;

    A* ap = &b;
    B* b1 = dynamic_cast<B*> (&a);  // NULL, because 'a' is not a 'B'
    B* b2 = dynamic_cast<B*> (ap);  // 'b'
    C* c = dynamic_cast<C*> (ap);   // NULL.

    A& ar = dynamic_cast<A&> (*ap); // Ok.
    B& br = dynamic_cast<B&> (*ap); // Ok.
    C& cr = dynamic_cast<C&> (*ap); // std::bad_cast
  }
</code>

If the value of ''object'' is a null pointer, then the result is a null pointer of type ''T''.


Related Topics: [[const_cast]], [[reinterpret_cast]], [[static_cast]], [[casting_comparison]]