04/11/231 VIT - SCSE

• In multiple inheritance, the constructors of base classes are invoked first, in order in which they appear in the declaration of the derived class.

• In multilevel inheritance, they are executed in the order of inheritance.

• Data member initialization is represented by

• Datamembername(value)• The value can be arguments of a constructor, expression

or other data members.

Constructors Invocation and Data Members Initialization

04/11/232 VIT - SCSE

class B{protected:int x,y;public:B(int a,int b):x(a),y(b) //x=a, y=b {}};class D:public B{private:int a,b;public:D(int p,int q,int r):a(p),B(p,q),b(r) {}

void output(){cout<<”x=”<<x<<endl;cout<<”y=”<<y<<endl;cout<<”a=”<<a<<endl;cout<<”b=”<<b<<endl;}};void main(){D ob(5,10,15);ob.output();}

04/11/233 VIT - SCSE

The following examples illustrate the initialization of data members with different formats: B(int a,int b):x(a),y(a+b)B(int a,int b):x(a),y(x+b)B(int a,int b):y(a),x(y+b)

04/11/234 VIT - SCSE

Overloaded member functions If the same member (data/function) exists in both the base class and the derived class, the member in the derived class will be executed. 

Abstract class Class with no objectUse for inheritance onlyCan derive classes from an abstract class

04/11/235 VIT - SCSE

class baseA{protected:int x;…..….};class derivedB:public baseA{protected:…..….};

class derivedD:public baseA{protected:…..….};class abc:public derivedB,public derived{…………};

Virtual Base Class Multipath inheritance

04/11/236 VIT - SCSE

• The data member x is inherited twice in the derived class abc, once through the derived class derivedB and again through derivedD.

• This is wasteful.• The above multiple repetition of the data member can be

corrected by changing the derived class derivedB and derivedD into virtual base classes.

• Any base class which is declared using the keyword virtual is called a virtual base class.

04/11/237 VIT - SCSE

class baseA{protected:int x;…..….};class derivedB:public virtual baseA{protected:…..….};

class derivedD:public virtual baseA{protected:…..….};class abc:public derivedB,public derivedD{…………};

04/11/238 VIT - SCSE

By making derivedB and derivedD into virtual base classes for abc, a copy of the data member x is available only once.

04/11/239 VIT - SCSE

class A{protected:int x;public:void getdata();void display();};class B:public virtual A{protected:float y;public:void getdata();void display();};

class C:public virtual A{protected:char name[20];public:void getdata();void display();};class D:public B,public C{public:void getdata();void display();};

04/11/2310 VIT - SCSE

void A:getdata(){cout<<”Enter an integer”;cin>>x;}void A:display(){cout<<”Integer:”<<x<,endl;}void B:getdata(){A::getdata();cout<<”Enter a floating point value”;cin>>y;}void B:display(){A::display();cout<<”Real Number:”<<y<<endl;}

void C:getdata(){A::getdata();cout<<”Enter a string”;cin>>name;}void C:display(){A::display();cout<<”String:”<<name<<endl;}void D:getdata(){B::getdata();C::getdata();}

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void D:display(){B::display();C::display();}void main(){D ob;ob.getdata();ob.display();}