Parameters-From Derived To Base Constructor

Parameters can be passed on to base class constructors from derived constructors. Given a base class BaseClass and a class derived from it DerivedClass: 
class DerivedClass: public BaseClass{};
by declaring the constructor of DerivedClass as: 
DerivedClass(string s2, string s3):BaseClass(s3){}
one specifies that the second parameter must be passed to the BaseClass constructor. For classes derived by multiple bases, the method to pass parameters to the bases is the same. The typical statement might look like: 
DerivedClass(string s2, string s3, int a, int b):BaseClass(s3),BaseClass1(a,b)


Example


#include <iostream>
#include <string>
using namespace std;

class BaseClass
{
     string b;
public:
     BaseClass(string s1)
     {
           b = s1;
           cout << "BaseClass constructor\n";
     }

     ~BaseClass()
     {
           cout << "BaseClass destructor\n";
     }
};

class DerivedClass: public BaseClass //
{
     string d;
public:
     DerivedClass(string s2, string s3):BaseClass(s3) // the
                                   // base constructor uses s3
     {
           d = s2;
           cout << "DerivedClass constructor\n";
     }

     ~DerivedClass()
     {
           cout << "DerivedClass destructor\n";
     }
};

int main()
{
    DerivedClass d("hi" , "hello");
}

Output

BaseClass constructor
DerivedClass constructor
DerivedClass destructor
BaseClass destructor