Computer Notes - Multiple Inheritance II

8/3/2019 Computer Notes - Multiple Inheritance II

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Multiple Inheritance

http://ecomputernotes.com


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A class can inherit from more thenone class



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Transmitter...

Transmit()

Receiver...

Receive()

Phone



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Example

class Phone: public Transmitter,public Receiver

{...

};



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Multiple Inheritance Derived class can inherit from public

base class as well as private andprotected base classes

class Mermaid:

private Woman, private Fish



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Multiple Inheritance The derived class inherits data

members and functions form all thebase classes

Object of derived class can performall the tasks that an object of base

class can perform



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Exampleint main(){

Phone obj;obj.Transmit();

obj.Receive();return 0;

}



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When using public multipleinheritance, the object of derived

class can replace the objects of allthe base classes



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Exampleint main(){

Phone obj;Transmitter * tPtr = &obj;

Receiver * rPtr = &obj;return 0;

}



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The pointer of one base class cannotbe used to call the function of

another base class The functions are called based on

static type



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Exampleint main(){

Phone obj;Transmitter * tPtr = &obj;

tPtr->Transmit();tPtr->Receive(); //Error

return 0;

}http://ecomputernotes.com


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Exampleint main(){

Phone obj;Receiver * rPtr = &obj;

rPtr->Receive();rPtr->Transmit(); //Error

return 0;

}http://ecomputernotes.com


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If more than one base class have afunction with same signature then

the child will have two copies of thatfunction

Calling such function will result inambiguity



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AmphibiousVehicle

Land Vehicle Water Vehicle

Car Boat



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Exampleclass LandVehicle{

public:int GetMaxLoad();

};class WaterVehicle{

public:

int GetMaxLoad();

};http://ecomputernotes.com


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Exampleclass AmphibiousVehicle:public LandVehicle,

public WaterVehicle{};

int main(){AmphibiousVehicle obj;

obj.GetMaxLoad(); // Error

return 0;

}



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Programmer must explicitly specifythe class name when calling

ambiguous function



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Exampleint main(){

AmphibiousVehicle obj;obj.LandVehicle::GetMaxLoad();

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

}



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The ambiguous call problem canarise when dealing with multiple level

of multiple inheritance



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AmphibiousVehicle


Vehicle

Car Boat



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Exampleclass Vehicle{

public:int GetMaxLoad();

};class LandVehicle : public Vehicle{

};

class WaterVehicle : public Vehicle{

};http://ecomputernotes.com


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public WaterVehicle{};

int main(){AmphibiousVehicle obj;

obj.GetMaxLoad(); // Error

return 0;}



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Exampleint main()

{AmphibiousVehicle obj;

obj.Vehicle::GetMaxLoad(); //Error

return 0;

}

Vehicle is accessible through two paths



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AmphibiousVehicle


Vehicle

Car Boat

Vehicle


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Exampleint main(){

AmphibiousVehicle obj;

obj.LandVehicle::GetMaxLoad();

obj.WaterVehicle::GetMaxLoad();

return 0;}



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Data member must be used withcare when dealing with more then

one level on inheritance



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protected:int weight;

};

class LandVehicle : public Vehicle{

};

class WaterVehicle : public Vehicle{

}; http://ecomputernotes.com


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public WaterVehicle{public:

AmphibiousVehicle(){

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

}

};

There are multiple copies of data memberweight http://ecomputernotes.com


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Memory View

Data Members of

Vehicle

Data Members of

LandVehicle

Data Members of AmphibiousVehicle

Data Members of

Vehicle

Data Members of

WaterVehicle



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Virtual Inheritance

In virtual inheritance there is exactlyone copy of the anonymous base

class object



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protected:

int weight;};

class LandVehicle :

public virtual Vehicle{};

class WaterVehicle :

public virtual Vehicle{

};



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Example

class AmphibiousVehicle:

public LandVehicle,public WaterVehicle{

public:

AmphibiousVehicle(){

weight = 10;

}

}; http://ecomputernotes.com


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Memory View

Data Members of Vehicle

Data Members ofLandVehicle

Data Members of AmphibiousVehicle

Data Members ofWaterVehicle



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Virtual Inheritance

Virtual inheritance must be used

when necessary There are situation when

programmer would want to use two

distinct data members inherited from

base class rather then one



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Example

Student

BS Student MS Student PhD Student

MS/PhD Student

GPA

Computer Notes - Multiple Inheritance II

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