On Apr 3, 5:42 pm, "dragoncoder" <pktiw...@gmail.com> wrote:
Hello experts,
I was just playing around wrote this code.
sundev1:/home/ptiwary/rnd $ cat a1.cpp
#include <iostream>
using namespace std;
class Base
{
public:
virtual void foo() { cout << "In Base::foo()" << endl; bar();}
// Since you are using Base pointers and allocating Derived objects
with new,
// the destructor must be virtual or you'll get memory leaks
virtual ~Base() { std::cout << "virtual ~Base\n"; }
private:
void bar() { cout << "In Base::bar()" << endl; }
};
class Der1: public Base
{
public:
virtual void foo() { cout << "In Der1::foo()" << endl; bar();}
private:
void bar() { cout << "In Der1::bar()" << endl; }
// to test the theory above:
~Der1() { std::cout << "virtual ~Der1()\n"; }
};
class Der2: public Base
{
public:
virtual void foo() { cout << "In Der2::foo()" << endl; bar();}
private:
void bar() { cout << "In Der2::bar()" << endl; }
};
int main()
{
Base* b1 = new Base();
Base* b2 = new Der1();
Base* b3 = new Der2();
b1->foo();
b2->foo();
b3->foo();
delete b1;
delete b2;
delete b3;
return 0;
}
sundev1:/home/ptiwary/rnd $ g++ a1.cpp
sundev1:/home/ptiwary/rnd $ ./a.out
In Base::foo()
In Base::bar()
In Der1::foo()
In Der1::bar()
In Der2::foo()
In Der2::bar()
I have 2 questions regarding this.
1. Is the behaviour correct? Because someone told me I need to make
bar() also virtual to get the effect.
Yes its correct. bar() needs not be virtual.
2. What is the deal with private virtual functions? Even if I make
bar() virtual, as its private, it won't be accessible from the derived
classes Der1 and Der2 so it does not make any sense having private
virtual functions. Am I right?
Not neccesarily, make the bar() functions public, the virtual foo()
functions private, invoke the private virtual foo() in bar(). You can
still have the derived object call the base's foo() by calling its
public interface ( Base::bar() ).- Hide quoted text -
- Show quoted text -- Hide quoted text -
- Show quoted text -
foo() is public in base. But ultimately it calls Derived version of
this function which is private in derived class. Isn't it access