Users' questions

Is Typeid an operator?

Is Typeid an operator?

The typeid operator provides a program with the ability to retrieve the actual derived type of the object referred to by a pointer or a reference. The typeid operator returns an lvalue of type const std::type_info that represents the type of expression expr. …

What is the use of Typeid operator?

The typeid operator allows the type of an object to be determined at run time. The result of typeid is a const type_info& . The value is a reference to a type_info object that represents either the type-id or the type of the expression, depending on which form of typeid is used.

What does Typeid mean in C++?

typeid is an operator in C++. It is used where the dynamic type or runtime type information of an object is needed. It is included in the library. Hence inorder to use typeid, this library should be included in the program. The typeid expression is an lvalue expression.

Does Typeid require RTTI?

Just like dynamic_cast, the typeid does not always need to use RTTI mechanism to work correctly. If the argument of the typeid expression is non-polymorphic type, then no runtime check is performed. Instead, the information about the type is known at the compile-time.

What does Typeid Return name?

The typeid operator returns an lvalue of type const type_info that represents the type of our value. An lvalue has an address that your program can access.

What happens when you perform a dynamic_cast?

If the cast is successful, dynamic_cast returns a value of type new-type. If the cast fails and new-type is a pointer type, it returns a null pointer of that type. If the cast fails and new-type is a reference type, it throws an exception that matches a handler of type std::bad_cast.

How do you use Typeid?

To use the typeid operator in a program, one needs to include the library header . It returns the lvalue of type const type_info to represent the type of value. Expression of typeid is an lvalue expression (lvalue has the address which is accessible by the program.

Why do we need dynamic_cast in C++?

The primary purpose for the dynamic_cast operator is to perform type-safe downcasts. The dynamic_cast operator ensures that if you convert a pointer to class A to a pointer to class B , the object of type A pointed to by the former belongs to an object of type B or a class derived from B as a base class subobject.

What happens when dynamic_cast fails?

If a dynamic_cast fails, the result of the conversion will be a null pointer. Because we haven’t checked for a null pointer result, we access d->getName(), which will try to dereference a null pointer, leading to undefined behavior (probably a crash).