Constructor in Derived Class

mahendragohil.gohil@gmail.com

Base class constructors are always called using the derived class constructors. 

Whenever you create derived class object, first the base class default constructor is executed and then the derived class’s constructor finishes execution.

In inheritance constructor of base class is inherited like other member functions. Object of derived class, access the constructor of base class like normal functions.

Example:

class Base
{ 
    int x;
    public:
    // default constructor
    Base() 
    { 
        cout<<"Base default constructor\n"; 
    }
};
class Derived:public Base
{ 
    int y;
    public:
    // default constructor
    Derived() 
    { 
        cout << "Derived default constructor\n"; 
    }
        Derived(int i) 
    { 
        cout << "Derived parameterized constructor\n"; 
    }
};
int main()
{
    Base b;        
    Derived d1;    
    Derived d2(10);
}

Output:

Base default constructor     //using object b
Base default constructor     // using derived class object d1
Derived default constructor  // using derived class object d1
Base default constructor    //using derived class object d2
Derived parameterized constructor //using derived class object d2

Note: Using derived class constructor you can supply the argument to the base class constructor. It follows the deriving order in which they are mentioned.

Method of InheritanceOrder of Execution
Class B:public AA(); base constructor
{B(); derived constructor
}; 
Class A:public B, public CB(); base constructor(first)
{C(); base constructor(second)
};A(); derived constructor(third)
Class A:public B, virtual public CC(); virtual base constructor (first)
{B(); ordinary base constructor(second)
};A(); derived constructor(third)

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