2.2 Constructor

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Introduction To OOP1.0

Classes And Objects

2.0

Inheritance and Polymorphism3.0

Exception handling4.0

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2009 | PN NORHASLIZA BT MUHAMAD NOR


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Define Constructor1

Characteristics ofConstructor2

Differentiate the types ofConstructor3

Use constructor in Program4

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1. A constructor is a member (method/function) that is called automatically each time when

an object is created.

2. The constructor allocates sufficient memory space for the object.

3. C++ will automatically supply a constructor if it is not supplied .

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1. Constructor has the same name as the class. For example constructor for class Employee

is declared as:

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class Employee{public:

Employee ( ); /* pengisytiharanconstructor */

};

Nama kelas

Nama method constructor



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2. The constructors task is to built and create object in memory. However a constructor

does not return a value.

3. An argument can be sent to the constructor

4. The constructor is called automatically when an object is created.This means, we dont

have to invoke it like other functions.



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1.Default Constructor

2.Parameterized Constructor

3.Initialization Constructor

4.Copy Constructor

5.Overloading Constructor



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1. Does not require any value (parameter).

2. Only have to declare the object.

3. C++ will automatically supply a constructor if it is not supplied.

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1

. fa lt str ct r

Secara automatik,

pengisytiharan objek ini akan

menyebabkan aturcara

memperuntukkan ruang

memori untuk objek box1.Untuk mewujudkan beberapa

objek, kelas harus mempunyai

constructorlalai.

NOTA

#includeclass box {private:

float length, width;public:box ( ); // default constructorvoid input( );void area ( );

};void main(){boxbox1; // pengistiharan kelas}

Method constructor tidak menerima sebarang nilai



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1. A constructor can have many parameters.

2. If the constructor receives a parameter, when the object is created the parameter must be

included with the declaration of the object.

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2

. ara t riz str ct r

#includeclass SegiEmpat{int panjang,lebar;public:SegiEmpat(int a, int b):panjang(a),lebar(b){}int kira_luas(){return panjang * lebar;}};void main(){int m,n;coutm;coutn;SegiEmpat S(m,n);cout


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1. The value is entered after an argument list for function, starting with single point ( : )

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3.I itializati str ct r

class SegiEmpat{

protected:int panjang,lebar;

public:// method constructor

SegiEmpat ():panjang(10),lebar(20){}};

y Data panjang akan diberikan nilai 10 manakala nilai data lebar akan diberikan

nilai 20.

y { } masih diperlukan.

PENERANGAN



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The example of a program is to calculate the area of a rectangle based on the value given on methodconstructor.

#includeclass SegiEmpat{int panjang,lebar;public:SegiEmpat():panjang(10),lebar(20){}

int kira_luas(){return panjang * lebar;}};void main()

{SegiEmpat a;cout


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1. Changing the private data value through a constructor.

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4. y str ct r

SegiEmpat a (1,2);SegiEmpat b(a);

Objek b akan menyalin nilai yang

dimiliki oleh objek a



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#include

class SegiEmpat{int panjang,lebar;public:SegiEmpat(int a, int b):panjang(a),lebar(b){}int kira_luas(){return panjang * lebar;}

};

void main(){int m,n;coutm;coutn;SegiEmpat S(m,n);

SegiEmpat Z(S);cout


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#include

class SegiEmpat{int panjang,lebar;public:SegiEmpat(int a, int b):panjang(a),lebar(b){}int kira_luas(){return panjang * lebar;}

};

void main(){int m,n;coutm;coutn;

SegiEmpat S(m,n);//SegiEmpat Z(S);cout


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#include

class SegiEmpat{

int panjang,lebar;public:SegiEmpat(){panjang=0;lebar=0;}

SegiEmpat(SegiEmpat & T){panjang=T.panjang;lebar=T.lebar;}

void SetData(int a,int b){panjang=a;lebar=b;}

int kira_luas(){return panjang * lebar;}};

Method constructor

salinan

Selain itu, anda sebagai pengaturcara juga boleh menakrifkan sendiri

method constructor salinan jika anda mahu.

Contoh : Menakrifkan fungsi constructor.

void main(){int m,n;coutm;coutn;

SegiEmpat a;a.SetData(m,n);SegiEmpat b(a);cout


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1. Just like other methods, constructor can also be overloaded.

2. You only have to list down all the different version of constructor needed to be used in

the class.

3. The main purpose of overloading a constructor is to provide options or give the object

initial value or not.

4. For example, in the following program, o1 will be given initial value but not for o2.

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5. v rl a i g str ct r



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#includeclass SegiEmpat_Sama{int panjang ;public:

SegiEmpat_Sama ( ) { panjang = 5; }SegiEmpat_Sama ( int n ) { panjang=n;}int luas(){return panjang*panjang;}};int main(){SegiEmpat_Sama o1(10); /* isytiharkan

objek dengan nilai awalan */

SegiEmpat_Sama o2; /* isytiharkantanpa nilai Awalan */

cout

2.2 Constructor

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