Object Oriented Programming (OOP) - CS304 Power Point Slides Lecture 27

8/13/2019 Object Oriented Programming (OOP) - CS304 Power Point Slides Lecture 27

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Object-Oriented Programming

(OOP)Lecture No. 27


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Class Collection

class Collection {...

public:

void AddElement(int);

bool SearchElement(int);

bool SearchElementAgain(int);bool DeleteElement(int);

};


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Class Set

class Set: private Collection {private:

...

public:

void AddMember(int);

bool IsMember(int);bool DeleteMember(int);

};


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Specialization (Restriction)

the derived class is behaviourallyincompatible with the base class

Behaviourally incompatible

means that base class cant

always be replaced by the derivedclass


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Specialization (Restriction)

Specialization (Restriction) can beimplemented using private and

protected inheritance


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ExampleSpecialization

(Restriction)Person

age : [0..125]

Adultage : [18..125]

setAge( a )

setAge( a )

age = a

If age < 18 then

errorelse

age = a


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Exampleclass Person{

protected:

int age;

public:bool SetAge(int _age){

if (_age >=0 && _age


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Example

class Adult : private Person {public:

bool SetAge(int _age){

if (_age >=18 && _age


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Private Inheritance

Only member functions and friendfunctions of a derived class can

convert pointer or reference of

derived object to that of parentobject


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Example

void DoSomething(const Parent &);

Child::Child(){

Parent & pPtr =

static_cast(*this);

DoSomething(pPtr);// DoSomething(*this);

}


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Private Inheritance

The child class object has ananonymous object of parent class

object

The default constructor and copy

constructor of parent class are

called when needed


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Exampleclass Parent{

public:

Parent(){

cout


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Exampleclass Child: private Parent{

public:Child(){

cout


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Example

int main() {Child cobj1;

Child cobj2 = cobj1;//Child cobj2(cobj1);

return 0;

}


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Example

Output:

Parent ConstructorChild Constructor

Parent Copy Constructor

Child Copy Constructor


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Private Inheritance

The base class that is more thenone level down the hierarchy

cannot access the member

function of parent class, if we areusing private inheritance


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Class Hierarchyclass GrandParent{

public :

void DoSomething();

};

class Parent: private GrandParent{

void SomeFunction(){

DoSomething();}

};


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Example

class Child: private Parent{

public:Child() {

DoSomething(); //Error

}

};


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Private Inheritance

The base class that is more thenone level down the hierarchy

cannot convert the pointer or

reference to child object to that ofparent, if we are using private

inheritance


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Class Hierarchy

void DoSomething(GrandParent&);class GrandParent{

};class Parent: private GrandParent{

public:

Parent() {DoSomething(*this);}

};


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Example

class Child: private Parent {public:

Child(){

DoSomething(*this); //Error

}

};


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Protected Inheritance

Use protected inheritance if youwant to build class hierarchy

using implemented in terms of


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If B is a protected base and D isderived class then public and

protected members of B can be

used by member functions andfriends of classes derived from D


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Class Hierarchyclass GrandParent{

public :

void DoSomething();

};

class Parent: protected GrandParent{

void SomeFunction(){

DoSomething();}

};


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Example

class Child: protected Parent{

public:

Child()

{

DoSomething();}

};


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If B is a protected base and D isderived class then only friends

and members of D and friends

and members of class derivedfrom D can convert D* to B* or D&

to B&


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Class Hierarchy

void DoSomething(GrandParent&);

class GrandParent{

};

class Parent: protectedGrandParent{

};


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Example

class Child: protected Parent {public:

Child()

{

DoSomething(*this);

}

};

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Object Oriented Programming (OOP) - CS304 Power Point Slides Lecture 27