Multiple Inheritance - Constructors And Destructors

In case of a class inheriting from more classes, the order of construction is: bases first, in the order in which they are declared, derived class later. So, given a class A derived both from B and C: 
class A: public B, public C
B’s constructor is called first, then C’s is called and finally A’s. For destructors the opposite order is followed. In the program below three different classes are declared: BaseClass1, BaseClass2 and DerivedClass, which inherits from BaseClass1 and BaseClass2. In order to show the order of constructor and destructor execution, each constructor and destructor prints a message to the console.

Example


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

class BaseClass1
{
public:
     BaseClass1()
     {
           cout << "BaseClass1 constructor\n";
     }

     ~BaseClass1()
     {
           cout << "BaseClass1 destructor\n";
     }
};

class BaseClass2
{
public:
     BaseClass2()
     {
           cout << "BaseClass2 constructor\n";
     }

     ~BaseClass2()
     {
           cout << "BaseClass2 destructor\n";
     }
};

class DerivedClass: public BaseClass1, public BaseClass2
{
public:
     DerivedClass()
     {
           cout << "DerivedClass constructor\n";
     }

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

int main()
{
DerivedClass d;
}

Output

DerivedClass destructor
BaseClass2 destructor
BaseClass1 destructor