#include <iostream>
#include <string>
using namespace std;
class Base {
public:
Base(const string& s): str(s) {cout<<"Base::ctor\n";}
Base(const Base& b): str(b.str) {cout<<"Base::copy ctor\n";}
virtual ~Base() {cout<<"Base::dtor\n";}
void f1() {cout<<"Base::f1()\n"; f2();} //2 orders
virtual void f2() {cout<<"Base::f2()\n";}
private:
string str;
};
class Derived : public Base {
public:
Derived(const string& s): Base(s)
{cout<<"Derived::ctor\n";}
Derived(const Derived& d): Base(d)
{cout<<"Derived::copy ctor\n";}
~Derived() {cout<<"Derived::dtor\n";}
virtual void f1() {cout<<"Derived::f1()\n"; f2();}
void f2() {cout<<"Derived::f2()\n"; f1();} //jumps from here to Leaf's f1()
};
class Leaf : public Derived {
public:
Leaf(const string& s): Derived(s)
{cout<<"Leaf::ctor\n";}
Leaf(const Leaf& dd): Derived(dd)
{cout<<"Leaf::copy ctor\n";}
~Leaf() {cout<<"Leaf::dtor\n";}
void f1() {cout<<"Leaf::f1()\n"; f3();}
void f3() {cout<<"Leaf::f3()\n";}
};
int main() {
Leaf * p = new Leaf("Hello");
Base * p2 = new Leaf(*p);
p2->f1();
delete p2;
delete p;
return 0;
}
Hello,
This question is an exam phrased one but it's very hard for me to find the right way to describe it and look for it online.
in line :
p2->f1();
the output is:
Base::f1()
Derived::f2()
Leaf::f1()
Leaf::f3()
in Derived f2() there's a call for f1(). who's going to be called? f1() of the type Base or f1() of Leaf? From what I have been taught, the compiler always looks for the function in the type to the left. (Base* p2 = new Leaf(*p) ) But over here I can see that it goes to f1() of class Leaf. I can see that it is Leaf's but don't understand why...
thanks for the helpers !
To answer your question quickly: Derived::f1() is called in Derived::f2().
To understand why it's Derived::f1() that's called, you probably need the knowledge of "C++ name hiding in inheritance", which you can refer to some online articles like:
You also need the knowledge of the "Unqualified name lookup" which you can refer to the "Member function definition" section in this web page: Unqualified name lookup.
In summary, the major points are:
The process of the call should be as follows:
p2->f1(); is executed.