C++ prgms 5th unit (inheritance ii)

Inheritance – II UNIT - 5
1 | P a g e A n a n d a K u m a r H N
Constructors, Destructors and Inheritance:
“Constructors are called in the order of
derivation and destructor are called in the
reverse order of derivation”
/*constructor and destructor in “simple
inheritance” when BASE class object is
created*/
#include<iostream>
using namespace std;
class base
{
public:
base( )
{
cout<<"base class constructor"<<endl;
}
~base( )
{
cout<<"base class destructor"<<endl;
}
};
class derived: public base
{
public:
derived( )
{
cout<<"derived class constructor”<<endl;
}
~derived( )
{
cout<<"derived class destructor”<<endl;
}
};
int main( )
{
base b1; //object of base class is created
}
OUTPUT:
base class constructor
base class destructor
inheritance” when DERIVED class object is
created*/
#include<iostream>
class base
{
public:
base( )
{
}
~base( )
{
}
};
{
public:
derived( )
{
cout<<"derived class constructor"<<endl;
}
~derived( )
{
cout<<"derived class destructor"<<endl;
}
};
int main( )
{
derived d1; //object of derived class is
created
}
OUTPUT:

inheritance” when BOTH BASE and
DERIVED classes object are created*/
#include<iostream>
class base
{
public:
base( )
{
}
~base( )
{
}
};
{
public:
derived( )
{
}
~derived( )
{
cout<<"derived class destructor"<<endl;
}
};
int main( )
{
base b1;
derived d1;
}
OUTPUT:
/*constructor and destructor in “Multilevel
inheritance” */
#include<iostream>
class base
{
public:
base( )
{
}
~base( )
{
}
};
class derived1: public base
{
public:
derived1( )
{
cout<<"derived1 class constructor"<<endl;
}
~derived1( )
{
cout<<"derived1 class destructor"<<endl;
}
};
class derived2: public derived1
{
public:
derived2( )
{
cout<<"derived2 class constructor"<<endl;
}
~derived2( )
{
cout<<"derived2 class destructor"<<endl;
}
};
int main( )
{
derived2 d2;
}
OUTPUT:

/*two parameters for constructor*/
#include<iostream>
class base
{
public:
int i,j;
base(int x,int y) //two parameters
{
i=x;
j=y;
}
};
class derived:public base
{
public:
int m,n;
derived(int p,int q,int r,int s):base(r,s)
{
m=p;
n=q;
}
void show()
{
cout<<i<<endl<<j<<endl;
cout<<m<<endl<<n<<endl;
}
};
int main()
{
derived d1(111,20,33,99);
d1.show();
}
OUTPUT:
base class constructor
derived class constructor
33
99
111
20
/*Passing parameter to base class
constructor in MULTIPLE inheritance*/
#include<iostream>
class base1
{
public:
int i;
base1(int x)
{
cout<<"base1 class constructor"<<endl;
i=x;
}
};
class base2
{
public:
int j;
base2(int y)
{
cout<<"base2 class constructor"<<endl;
j=y;
}
};
class derived:public base1,public base2
{
int k;
public:
derived(int p,int q,int r):base1(q),base2(r)
{
k=p;
}
void show()
{
cout<<i<<endl;
cout<<j<<endl;
cout<<k<<endl;
}
};
int main()
{
derived d1(111,20,33);
d1.show();
}
OUTPUT:
Base1 class constructor
Base2 class constructor
derived class constructor
20
33
111

Granting access:
#include<iostream>
class base
{
private:
int a,b;
public:
void initbase(int x,int y)
{
a=x;
b=y;
}
void showbase()
{
cout<<"a="<<a<<" b="<<b<<endl;
}
};
class derived: private base
{
private:
int m,n;
public:
base::initbase; //initbase is public again
base::showbase; //showbase is public again
void initderived(int u,int v)
{
m=u;
n=v;
}
void showderived()
{
cout<<"m="<<m<<" n="<<n<<endl;
}
};
int main()
{
derived d1;
d1.initbase(77,99);
d1.showbase();
d1.initderived(33,44);
d1.showderived();
}
/* ambiguous in diamond (or) multiple
inheritance*/
#include<iostream>
class A
{
public:
int i;
};
class B : public A
{
public:
int j;
};
class C: public A
{
public:
int k;
};
class D: public B, public C
{
public:
int sum;
};
int main()
{
D ob;
ob.i = 10; //ambiguous since two copies of
i is inherited ERROR
ob.j = 20;
ob.k = 30;
ob.sum = ob.i + ob.j + ob.k; //ERROR
cout<<"Value of i is : "<<ob.i; //ERROR
cout<<"Value of j is : ”"<< ob.j;
cout << "Value of k is :”"<< ob.k;
cout << "“Sum is : ”"<< ob.sum;
return 0;
}

/* Solving Multiple Inheritance ambiguity
by using : : operator */
#include<iostream>
class A
{
public:
int i;
};
class B : public A
{
public:
int j;
};
class C: public A
{
public:
int k;
};
{
public:
int sum;
};
int main()
{
D ob;
ob.B::i = 10; //unambiguous
ob.C::i=100; //unambiguous
ob.j = 20;
ob.k = 30;
ob.sum = ob.B::i + ob.j + ob.k; //unambiguous
cout<<"Value of i is in B: "<<ob.B::i<<endl;
cout<<"Value of i is in C: "<<ob.C::i<<endl;
cout<<"Value of j is : "<< ob.j<<endl;
cout << "Value of k is :"<< ob.k<<endl;
cout << "Sum is : "<< ob.sum<<endl;
return 0;
}
OUTPUT:
Virtual base classes / Inheritance:
Example 1:
#include<iostream>
class A
{
public:
int i;
};
class B : public virtual A
{
public:
int j;
};
class C: public virtual A
{
public:
int k;
};
{
public:
int sum;
};
int main()
{
D ob;
ob.i = 10;//unambiguous since one copy of i is
inherited.
ob.j = 20;
ob.k = 30;
ob.sum = ob.B::i + ob.j + ob.k;
cout<<"Value of i is in B: "<<ob.B::i<<endl;
cout<<"Value of i is in C: "<<ob.C::i<<endl;
cout<<"Value of i in A : "<<ob.A::i<<endl;
cout<<"Value of j is : "<< ob.j<<endl;
cout << "Value of k is :"<< ob.k<<endl;
cout << "Sum is : "<< ob.sum<<endl;
return 0;
}
OUTPUT:

Example 2: Virtual Base Inheritance
#include<iostream>
class stuinfo
{
public:
int usn;
char name[20];
void readinfo()
{
cout<<"enter student usn and namen";
cin>>usn>>name;
}
};
class theoryscore : public virtual stuinfo
{
public:
int t1,t2,t3;
void readtheoryscore()
{
cout<<"enter student score in t1,t2 and t3n";
cin>>t1>>t2>>t3;
}
};
class labscore: public virtual stuinfo
{
public:
int L1,L2;
void readlabscore()
{
cout<<"enter student score in L1 and L2n";
cin>>L1>>L2;
}
};
class result: public theoryscore, public labscore
{
public:
void show()
{
cout<<"Student details are:n";
cout<<"usn:"<<usn<<endl; //one copy of usn;
cout<<"name:"<<name<<endl; //one copy of name;
cout<<"marks1:"<<t1<<endl;
cout<<"lab1:"<<L1<<endl;
cout<<"lab2:"<<L2<<endl;
}
void avgresult()
cout<<"average marks in theory is:"<<
(t1+t2+t3)/3.0<<endl;
cout<<"average marks in LAB is:"<<
(L1+L2)/2.0<<endl;
}
};
int main()
{
result obj;
obj.readinfo();// one copy of readinfo() function
obj.readtheoryscore();
obj.readlabscore();
obj.show();
obj.avgresult();
}

C++ prgms 5th unit (inheritance ii)

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