Object Oriented Programming (OOP) - CS304 Power Point Slides Lecture 31

8/13/2019 Object Oriented Programming (OOP) - CS304 Power Point Slides Lecture 31

1/35

Object-Oriented Programming

(OOP)Lecture No. 31


2/35

Multiple Inheritance

A class can inherit from morethen one class


3/35


Transmitter...

Transmit()

Receiver...

Receive()

Phone


4/35

Example

class Phone: public Transmitter,public Receiver

{...};


5/35


Derived class can inherit frompublic base class as well asprivate and protected baseclasses

class Mermaid:private Woman, private Fish


6/35


The derived class inherits datamembers and functions form allthe base classes

Object of derived class canperform all the tasks that an

object of base class can perform


7/35

Example

int main(){Phone obj;

obj.Transmit();obj.Receive();return 0;

}


8/35


When using public multipleinheritance, the object of derivedclass can replace the objects ofall the base classes


9/35

Example


Transmitter * tPtr = &obj;Receiver * rPtr = &obj;return 0;

}


10/35


The pointer of one base classcannot be used to call thefunction of another base class

The functions are called based on

static type


11/35

Example


Transmitter * tPtr = &obj;tPtr->Transmit();tPtr->Receive(); //Error return 0;

}


12/35

Example


Receiver * rPtr = &obj;rPtr->Receive();rPtr->Transmit(); //Error return 0;

}


13/35


If more than one base class havea function with same signaturethen the child will have two copiesof that function

Calling such function will result inambiguity


14/35


AmphibiousVehicle

Land Vehicle Water Vehicle

Car Boat


15/35

Example

class LandVehicle{public:

int GetMaxLoad();};class WaterVehicle{

public:int GetMaxLoad();

};


16/35

Exampleclass AmphibiousVehicle:

public LandVehicle,public WaterVehicle{

};int main(){ AmphibiousVehicle obj;

obj.GetMaxLoad(); // Errorreturn 0;}


17/35


Programmer must explicitlyspecify the class name whencalling ambiguous function


18/35

Example

int main(){ AmphibiousVehicle obj;

obj.LandVehicle::GetMaxLoad();obj.WaterVehicle::GetMaxLoad();return 0;

}


19/35


The ambiguous call problem canarise when dealing with multiplelevel of multiple inheritance


20/35


AmphibiousVehicle


Vehicle

Car Boat


21/35

Example

class Vehicle{public:

int GetMaxLoad();};class LandVehicle : public Vehicle{

};class WaterVehicle : public Vehicle{};


22/35



};int main(){ AmphibiousVehicle obj;

obj.GetMaxLoad(); // Errorreturn 0;}


23/35

Example

int main(){ AmphibiousVehicle obj;obj.Vehicle::GetMaxLoad(); //Errorreturn 0;

} Vehicle is accessible through two

paths


24/35


AmphibiousVehicle


Vehicle

Car Boat

Vehicle


25/35

Example

int main(){ AmphibiousVehicle obj;obj.LandVehicle::GetMaxLoad();obj.WaterVehicle::GetMaxLoad();

return 0;}


26/35


Data member must be used withcare when dealing with more thenone level on inheritance


27/35

Example

class Vehicle{protected:

int weight;};class LandVehicle : public Vehicle{

};class WaterVehicle : public Vehicle{};


28/35



public: AmphibiousVehicle(){

LandVehicle::weight = 10;WaterVehicle::weight = 10;

}}; There are multiple copies of data member

weight


29/35

Memory View

Data Members ofVehicle

Data Members ofLandVehicle

Data Members of AmphibiousVehicle

Data Members ofVehicle

Data Members ofWaterVehicle


30/35

Virtual Inheritance

In virtual inheritance there isexactly one copy of theanonymous base class object


31/35

Exampleclass Vehicle{protected:

int weight;};

class LandVehicle :public virtual Vehicle{

};

class WaterVehicle :public virtual Vehicle{};


32/35


33/35

Memory View

Data Members of Vehicle

Data Members ofLandVehicle

Data Members of AmphibiousVehicle

Data Members ofWaterVehicle


34/35

Virtual Inheritance

Virtual inheritance must be usedwhen necessary There are situation when

programmer would want to usetwo distinct data members

inherited from base class ratherthen one


35/35

Example

Student

BS Student MS Student PhD Student

MS/PhD Student

GPA

Documents

Object Oriented Programming (OOP) - CS304 Power Point Slides Lecture 31