Type introspection is the ability of a programming language to examine and manipulate the types of objects at runtime. It allows developers to access information about the types, such as their names, relationships, and attributes. C++ does not have built-in support for type introspection like some other languages, but there are several techniques that can be used to achieve similar functionality. In this blog post, we will explore some of the basics of type introspection in C++.

Using typeid operator

One way to perform type introspection in C++ is by using the typeid operator. The typeid operator allows you to obtain information about the type of an object at runtime. It returns a reference to a type_info object, which contains the name and other information about the type.

Here’s an example code snippet that demonstrates the use of typeid operator:

#include <iostream>
#include <typeinfo>

class Base {
    // Some class definition
};

int main() {
    Base obj;
    const std::type_info& type = typeid(obj);
    std::cout << "Object type: " << type.name() << std::endl;

    if (type == typeid(Base)) {
        std::cout << "Object is of type Base" << std::endl;
    }
    return 0;
}

In this example, we create an object obj of type Base. We then use the typeid operator to get the type_info object which represents the type of obj. We can access the name of the type using the name() member function of the type_info object. Finally, we compare the obtained type with another type using the == operator.

Using RTTI (Run-Time Type Information)

Another way to achieve type introspection in C++ is by using RTTI (Run-Time Type Information). RTTI provides a set of features that allow you to determine the dynamic type of an object and perform type casts at runtime.

Here’s an example code snippet showing the use of RTTI:

#include <iostream>
#include <typeinfo>

class Base {
public:
    virtual ~Base() {}
};

class Derived : public Base {
    // Some derived class definition
};

int main() {
    Base* basePtr = new Derived();

    Derived* derivedPtr = dynamic_cast<Derived*>(basePtr);
    if (derivedPtr != nullptr) {
        std::cout << "Object is of type Derived" << std::endl;
    } else {
        std::cout << "Object is not of type Derived" << std::endl;
    }

    delete basePtr;
    return 0;
}

In this example, we have a base class Base and a derived class Derived. We create a pointer basePtr of type Base* pointing to an object of type Derived. We then use the dynamic_cast operator to perform a runtime type check. If the object pointed to by basePtr can be safely cast to Derived*, then the cast will succeed and the derivedPtr will point to the derived object. Otherwise, the dynamic_cast will return a null pointer.

To summarize, while C++ does not have direct support for type introspection, techniques like using the typeid operator and RTTI can be employed to achieve similar functionality. These techniques give developers the ability to examine and manipulate object types at runtime, providing more flexibility and control in their programs.

#C++ #TypeIntrospection