C++ ( Classes and pointers)

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#include <iostream>

class Base {
    virtual void method() {std::cout << "from Base" << std::endl;}
public:
    virtual ~Base() {method();}
    void baseMethod() {method();}
};

class A : public Base {
    void method() {std::cout << "from A" << std::endl;}
public:
    ~A() {method();}
};

int main(void) {
    Base* base = new A;
    base->baseMethod();
    delete base;
    return 0;
}

I can't understand why the output of this code is: from A from A from Base

Technically it should only print "from A " only.


Its called Upcast, take a look at the example in the link for more information. The first "from A" occurs when you execute:

 base->baseMethod();

The second "from A" when the destructor of A is called, and the "from Base" is printed when the destructor of Base is called.

C++ Pointer to Class Members, C" file, along with the code for the other class member functions. The copy constructor should copy the values of all non-pointer data members, and should copy  Learn From Top Ivy League Grads! Backed by 100% Money-Back Guarantee


base is object of type A, So base->baseMethod() will call A's implementation of virtual method method(), "from A" is printed, method() is called from the d'tors of A and base, When deleting an object in cpp it's d'tor is called and it's base class d'tor is called right after (the opposit when creating an object) so : "from A" "from base" is printed.

Classes with Pointer Data Members, P.S: Can someone guide me to a good tutorial of usage of pointers in C++, so that my queries like these can be directly addressed in it. share. Pointer to C++ Classes A pointer to a C++ class is done exactly the same way as a pointer to a structure and to access members of a pointer to a class you use the member access operator -> operator, just as you do with pointers to structures. Also as with all pointers, you must initialize the pointer before using it.


When we call base->baseMethod() it calls the Base::baseMethod as it not overriden by class A. baseMethod calls method function, as base is pointer of class A, it calls the A::method as it is overriden. Even though the method is private it follows the polymorphic behaviour.

When delete base is executed, first destructor of derived class is called because Base class destructor is virtual. Derived class destructor call it own method function. If we do not had virtual destructor then destructor of derived was not called and hence you have seen only one from A as output apeend by from base

After that it calls the base class destructor and this calls the method function of Base class only as derived class is already destructed.

C++ class object pointers and accessing member functions, 'this' pointer in C++. To understand 'this' pointer, it is important to know how objects look at functions and data members of a class. Each object gets its own copy  Defining a Pointer of Class type. We can define pointer of class type, which can be used to point to class objects. Here you can see that we have declared a pointer of class type which points to class's object. We can access data members and member functions using pointer name with arrow -> symbol.


C++ 23 - Classes and Pointers, Regular expressions library (C++11) Pointers to class objects may also appear as the left-hand operands of the member access operators  C - Pointers. Pointers in C are easy and fun to learn. Some C programming tasks are performed more easily with pointers, and other tasks, such as dynamic memory allocation, cannot be performed without using pointers. So it becomes necessary to learn pointers to become a perfect C programmer.


'this' pointer in C++, int A::b(int c) { }, Classes Pointers to base class. One of the key features of class inheritance is that a pointer to a derived class is type-compatible with a pointer  For this it is first necessary to know the concept of pointers & classes in C++. In general Pointers are variables that store address of other variables. A class in C++ is and Object oriented programming feature which enables programmer to create user defined complex datatypes (member variables) and functions(member functions) that operate on that data.


Pointer declaration, For this it is first necessary to know the concept of pointers & classes in C++. In general Pointers are variables that store address of other  Pointers in C/C++ with Examples Pointers are symbolic representation of addresses. They enable programs to simulate call-by-reference as well as to create and manipulate dynamic data structures. It’s general declaration in C/C++ has the format: