CPP/Classes/DownCasting - Revision history

Mikael.s.persson: /* DownCasting.cpp */

2010-11-24T02:14:07Z

‎DownCasting.cpp

Mikael.s.persson: /* Threads.cpp */

2010-11-24T02:13:22Z

‎Threads.cpp

Mikael.s.persson: DownCasting.cpp

2010-11-24T02:11:30Z

DownCasting.cpp

New page

==Threads.cpp==
<source lang="cpp">
#include <iostream>

class Base {
public:
virtual ~Base() { }; //at least one virtual function is necessary in the base class.
};

class Derived1 : public Base {
public:
Derived1() { };
~Derived1() { };
void print(); //notice that print does not exist in Base.
};

class Derived2 : public Base {
public:
Derived2() { };
~Derived2() { };
void print(); //notice that print does not exist in Base.
};

int main() {
Base* ptr1 = new Derived1();
Base* ptr2 = new Derived2();

//now we can try a dynamic down cast:
Derived1* ptr3 = dynamic_cast<Derived1*>(ptr1);
//if successful, ptr3 will be non-NULL:
if(ptr3)
ptr3->print();
else
std::cout << "Could not down-cast ptr1 to Derived1 class!" << std::endl;

//if we try with ptr2 it will not work because ptr2 is pointing to an object of class Derived2.
Derived1* ptr4 = dynamic_cast<Derived1*>(ptr2);
//if successful, ptr4 will be non-NULL:
if(ptr4)
ptr4->print();
else
std::cout << "Could not down-cast ptr2 to Derived1 class!" << std::endl;
};

void Derived1::print() {
std::cout << "Down cast to Derived1 was successful!" << std::endl;
};

void Derived2::print() {
std::cout << "Down cast to Derived2 was successful!" << std::endl;
};

</source>

@@ Line 1: / Line 1: @@
-==Threads.cpp==
+==DownCasting.cpp==
 <source lang="cpp">
 #include <iostream>

@@ Line 41: / Line 41: @@
    else
      std::cout << "Could not down-cast ptr2 to Derived1 class!" << std::endl;
 };