Dynamic_cast and static_cast in C++

C++Server Side ProgrammingProgramming

static_cast: This is used for the normal/ordinary type conversion. This is also the cast responsible for implicit type coersion and can also be called explicitly. You should use it in cases like converting float to int, char to int, etc. This can cast related type classes. If the types are not same it will generate some error.

Example

#include<iostream>
using namespace std;
class Base {};
class Derived : public Base {};
class MyClass {};
main(){
   Derived* d = new Derived;
   Base* b = static_cast<Base*>(d); // this line will work properly
   MyClass* x = static_cast<MyClass*>(d); // ERROR will be generated during compilation
}

Output

[Error] invalid static_cast from type 'Derived*' to type 'MyClass*'

dynamic_cast: This cast is used for handling polymorphism. You only need to use it when you're casting to a derived class. This is exclusively to be used in inheritance when you cast from base class to derived class.

Example

#include<iostream>
using namespace std;
class MyClass1 {
   public:
      virtual void print()const {
         cout << "This is from MyClass1\n";
      }
};
class MyClass2 {
   public:
      virtual void print()const {
         cout << "This is from MyClass2\n";
      }
};
class MyClass3: public MyClass1, public MyClass2 {
   public:
      void print()const {
         cout << "This is from MyClass3\n";
      }
};
int main(){
   MyClass1* a = new MyClass1;
   MyClass2* b = new MyClass2;
   MyClass3* c = new MyClass3;
   a -> print();
   b -> print();
   c -> print();
   b = dynamic_cast< MyClass2*>(a); //This cast will be failed
   if (b)
      b->print();
   else
      cout << "no MyClass2\n";
   a = c;
   a -> print(); //Printing from MyClass3
   b = dynamic_cast< MyClass2*>(a); //Successfully casting is done
   if (b)
      b -> print();
   else
      cout << "no MyClass2\n";
}

Output

This is from MyClass1
This is from MyClass2
This is from MyClass3
no MyClass2
This is from MyClass3
This is from MyClass3
raja
Published on 30-Apr-2019 11:37:49
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