Lecture01 Objectorientedprogramming 130120010815 Phpapp01 (1)

8/20/2019 Lecture01 Objectorientedprogramming 130120010815 Phpapp01 (1)

1/40

1

If you prefer to save your printer ink,follow the steps below to print the lecturesin black text on white background.

1. In PowerPoint, select File > Print.

2. In the ettings section, locate an ite!with value "#olor", change it to "Pure$lack and %hile".

&ip to ave Printer Ink &ip to ave Printer Ink


2/40

Introduction to

Object-Oriented

Programming

TCP1201 OOPDS 2

Lecture 1Lecture 1

http://fit.mmu.edu.my/


3/40

3

&o understand ob'ect ( class &o understand abstraction in #)) &o understand encapsulation in #))

&o categori*e si!ilar ob'ects &o categori*e ob'ects by #o!position &o understand ob'ect behaviors &o construct +- #lass iagra! &o di/erentiate between Procedural

Progra!!ing and 0b'ect0rientedProgra!!ing

-earning 0b'ectives-earning 0b'ectives


4/40

What is an “What is an “object object ”?”?

n object is a co!puter representationof realworld person, place, event oranything in the proble! that we aresolving.


5/40

5

What is an “What is an “object object ”?”?

n ob'ect consists of34 attributes /data/states/felds/variables 5typically

noun6, e.g. na!e, date, balance, si*e, !ark, etc.

4 behaviors /procedures/methods/operations/unction

s 5typically verb6, e.g. eat, drive, set, get, push, etc.%e refer to a group o similar objects with the

sa!e attributes and behaviors as a class.a!e attribute does not !ean sa!e value for

the attribute, e.g. 2 students have attribute7na!e7, but the na!e of each student can bedi/erent.


6/40

Object and ClassObject and Class#lass3 tudent.

ttributes3 na!e, student8I.$ehavior9!ethod3 do8ho!eworks56.

0b'ects of tudent class3 steve, victor.


7/40

Object and ClassObject and Classteve and victor share the sa!e attributes 5na!e (

student8id6, but each ob'ect has its own value for theattributes.


8/40

8

Object and ClassObject and Class

%e refer to a group o similar objects withthe sa!e attributes and behaviors as aclass.

&hus, we can de:ne a class as3

4 ;a set of objects comprised of thesame attributes and behaviors


9/40

9

Object-OrientedObject-Oriented

ProgrammingProgramming &he idea is to design a progra! to solve a proble! by co!bining both the data and

procedures 5!e!ber functions6 that operate on that data into a singe unit called ob'ect.

Popular 00P languages3 #)), =ava, #, ?$, etc.#)) in P12@1 focuses on 00P.

Data

Member

Function

Data

MemberFunction

Data

MemberFunction

Object1 Object3

Object2

Messages


10/40

10

Steps to Use OOPSteps to Use OOP

1. Identify the ob'ects in the proble!.2. Identify the data9attributes and

operations9!ethods in each ob'ect.A. eter!ine how the ob'ects interact with

one another 5!essaging6.

Data

Member

Function

Data

Member

Function

Data

Member

Function

Object1 Object3

Object2

Messages


11/40

11

Principles o! OOP Principles o! OOP

1. Abstraction 4 identify the properties that arei!portant to the user in the proble!, andcreate representations that are si!ilar to itsoriginal !eaning.

2. Encapsulation 4 co!bine data and itsoperations in a single unit, and hide thei!ple!entation fro! user.

3. Inheritance 4 create new classes fro! existing

classes 5-ecture A6.4. ol!morphism 4 use the sa!e expression to

denote di/erent operations 5-ecture B6.


12/40

12

OOP Principle "OOP Principle "

#bstraction#bstraction bstraction is the process of identifying

i!portant logical properties 5ob'ect,attributes, !ethods6 that si!pli:es the!odeling and working of the proble!.

If you are designing a !obile phone,exa!ple properties that are i!portant tothe user are the screen, keypad, +I,

cover, etc., but not the internal workingof the processor, how the screen isactually rendered, etc.

OOP P tt


13/40

13

OOP n Pract ce "n ract ce "#bstraction#bstraction

ssu!e that we are developing si!ple syste! to

keep track of sub'ects registered by student. Itwon7t be diCcult to identify the following tudentclass, its attributes and behaviors9!ethods.4 %e keep the class si!ple for the purpose of discussion.

Attributesid

sub'ects

"ethodsshow8sub'ectsregister8sub'ectwithdraw8sub'ect

#lass

tudent

OOP P tt


14/40

14

OOP n Pract ce "n ract ce "#bstraction#bstraction

$ased on what we collected and consider appropriate data type, the following class de:nition can be declared3

&he next step is to consider encapsulation 4 the 2nd 00P principle.class Student { int id;

vector subjects; void show_subjects(); void register_subject(); void withdraw_subject();};


15/40

15


$ncapsulation$ncapsulationDncapsulation is the idea that the internal

workings of an ob'ect can be hidden fro!the outside world.

Dncapsulation is perfor!ed in 2 ways3

–

%e encapsulate how attributes areaccessed via access privileges5private, public, protected, friend6.

– %e encapsulate how !ethods are

i!ple!ented by separating interfaceand i!ple!entation into di/erent :les.


16/40

16

#ccess Pri%ileges in C&ccess Pri%ileges in C&&ccess privileges allow us to restrict the

access to an ob'ectEs !e!bers.B types of access privileges in #))3

1.private

2.public3.protected 5-ecture A Inheritance6

4.friend 5-ecture 0perator 0verloading6


17/40

privateprivate andand publicpublic #ccess#ccessPri%ilegesPri%ileges

private !e!bers Got accessible fro!

anywhere except for

the ob'ect itself . %e generally declareattributes as private.

$y default, all!e!bers of a #))

class are declared asprivate ifunspeci:ed.

public !e!bers ccessible fro!

anywhere including

outside the class. %e generally declare!ethods as public.

$y default, all!e!bers of a #))

struct are declaredas public ifunspeci:ed.

17


18/40

18


$ncapsulation$ncapsulation &o !aintain data integrity, attribute is

usually set hidden9private inside a class toprevent direct !odi:cation fro! outside theclass.

&o access or !odify an ob'ect7 attribute fro!outside the class, we provide public get orset !ethods.

Het !ethod 4 a !ethod that returns thevalue of an attribute but does not !odify it.et !ethod 4 a !ethod that !odi:es the

value of an attribute.

OOP n Pract cen ract ce


19/40

19

OOP n Pract ce "n ract ce "$ncapsulation$ncapsulation

ince all our !ethods are !eant to be used fro! outside the class, we should declare the! as public.

&he next step is to consider where to place the i!ple!entation.class Student { // private by deault

int id; vector subjects; public! // public ro" now on int get#d(); // get "ethod or id void set#d (int id); // set "ethod or id void show_subjects(); void register_subject();

void withdraw_subject();};


20/40

20

Placing ImplementationPlacing Implementation &here are 2 ways to place the

i!ple!entation 5!ethod body6 in #)).

class Student {

int id;

$$$

int get#d(); //prototype

void set#d (int id); //prototype

$$$

}; // %nd o class

int Student!!get#d() {

return id;

}

void Student!!set#d (int id) {

this&>id ' id;

}

class Student {

int id;

$$$

int get#d() {

return id;

}

void set#d (int id) {

this&>id ' id;

}

$$$

}; // %nd o class

Inside o! class declarationOutside o! class declarati


21/40

21

Placing ImplementationPlacing Implementation

Outside o! Class 'eclarationOutside o! Class 'eclaration

"!!" is a scope resolution operator. "Student!!" indicates that the function is a

method of Student class, not a global function.

class Student { int id;

$$$

int get#d(); //prototype


$$$

}; // %nd o class

int Student!!get#d() {

return id;

}


this&>id ' id;}


22/40

22

(he(he thisthis PointerPointer

We use this pointer to refer to a member of aclass.

class Student {

int id;

$$$


$$$

}; // %nd o class

$$$


this&> id ' id;

}

id here is function parameter,

not attribute

id here is attribute


23/40

23

(he(he thisthis PointerPointer

We use this pointer to refer to a member of aclass.

class Student {

int id;

$$$ void set#d (int id); //prototype

$$$

}; // %nd o class

$$$


id ' id; // rong *para"eter ' para"eter*$

// +ttribute id is not updated$

this&> id ' id; // ,orrect *attribute ' para"eter*$

Student!!id ' id; // ,orrect *attribute ' para"eter*$

}


24/40

24

)aintaining 'ata Integrit* +ith)aintaining 'ata Integrit* +ith

$ncapsulation$ncapsulation

By declaring attributes as private and providingpublic set methods, we can prevent erroneousdata being entered into the object.

$$$// %nsure id entered is within range$


i (id < -......... id > 0000000000) {

cout id ' .;

} else

this&>id ' id;

}


25/40

25

Implementation in SeparateImplementation in Separate

,iles,ileso bring encapsulation to the ne!t level, we

separate the interfaces and its implementations

into different files.

For every class

# $lace its interface in a .hpp file # called header file, e.g.

%tudent.hpp.

# $lace its implementation in a .cpp file # called source

file, e.g. %tudent.cpp.

# &n every cpp that needs to refer to the class, "'include"

the hpp.


26/40

26

PP eader ,ilePP eader ,ilehe use of #ifndef, #define ( #endif is to

prevent multiple inclusion.

// Student$hpp header ile

2inde S345%63_788 // 8revent "ultiple inclusion$

2deine S345%63_788

2include


27/40

27

CPP Source ,ileCPP Source ,ile

)very cpp source file that needs to refer to theclass should "'include" the hpp.

// Student$cpp source ile

2include *Student$hpp* // 4se ** not $

int Student!!get#d() { return id; }void Student!!set#d (int id) { this&>id ' id; }void Student!!show_subjects() { $$$ }void Student!!register_subject() { $$$ }void Student!!withdraw_subject() { $$$ }

// "ain$cpp source ile2include *Student$hpp* // 4se ** not $

int "ain() { Student s; s$register_subject(); $$$

}


28/40

28

Wh* $ncapsulation?Wh* $ncapsulation?1. &o !aintain data integrity

4 $y li!iting direct access to attributes, we prevent classusers fro! providing invalid data to the ob'ect.

2. &o reduce the need for class users to worry aboutthe i!ple!entation4 $y separating the interface fro! the i!ple!entation

5shorter class declaration6, class users can focus on usingthe class instead of being bothered by the i!ple!entationof the class.

A. &o i!prove progra! !aintenance1.eparating the interface fro! the i!ple!entation enables

us to change the i!ple!entation without the class usersever being aware 5provided that the interface re!ains thesa!e6.


29/40

29

Categoriing ObjectsCategoriing Objects &here !ight be !any ob'ects.

2 co!!on ways to categori*e ob'ects are3

1. #ategori*e si!ilar ob'ects that have thesa!e attributes and behaviors, e.g. the

student exa!ple.4 %e have covered this one up until now.

2. #ategori*e ob'ects by co!position, that iswhen an attribute of a class is a class by

itself, e.g. a faculty has !any students.


30/40

30

Categoriing b* CompositionCategoriing b* Composition %hen categori*ing ob'ects by composition, an

attribute of a class is a class by itself. Is also referred to as a ;has$a< relationship.

Dxa!ple 13 faculty has !any students 5bothfaculty and student are classes6.

Dxa!ple 23 &ypical corporate organi*ation34 A classes can be identi:ed3 %ept& 'ta(& %ata.

4 %ept has 'ta( and %ata.

$ersonnel Data

$ersonnel%taff

Finance Data

Finance

%taff

%ales Data

%ales

%taff

Sales Dept. Finance Dept.

Personnel Dept.

Messages


31/40

31

Categoriing b* CompositionCategoriing b* Composition

%ample code for the composition involving facultyand student.

class Student { // Student is a class$

$$$

}; // %nd o class

class 9aculty { // 9aculty is a class$

string na"e;

vector students-; // ,o"position attribute is

// a class by itsel$

//vector students; // +lso co"position$ //Student students=-.; // +lso co"position$

//Student: students; // +lso co"position$

$$$

};


32/40

32

U)/ Class 'iagramU)/ Class 'iagram

)"* is a for!al notation to describemodels 5representations ofthings9ob'ects6 in sofware develop!ent.

#lass %iagram is one type of !anydiagra!s in +-.

#lass iagra! contains 2 ele!ents3

4 #lasses represent ob'ects with co!!onattributes, operations, and associations.

4 Associations represent relationships thatrelate two or !ore classes.


33/40

33

Class 'iagramClass 'iagram

ust have A sections.

#lass na!e is placed at the top section.

ttributes are placed at the !iddle section.

$ehaviors are placed at the botto! section.

77 denotes private access privilege.

7)7 denotes public access privilege.

7JK7 denotes "!any" 5array, vector6.

Student

id3intsub'ects3stringJK

)getId563int)setId5id3int63void)show8sub'ects563void)register8sub'ect563void)withdraw8sub'ect563void


34/40

34

Class 'iagramClass 'iagram

Associations shows the relationship betweeninstances of classes, e.g. a faculty has one or!ore students, a student belongs to exactly onefaculty only.

,acult*

na!e3stringstudents3tudentJK

)intake56

ssociation

1 1..n

7n7 !eans!any

Student

id3 intsub'ects3stringJK

)getId563int)setId5id3int63void)show8sub'ects563void)register8sub'ect563void

)withdraw8sub'ect563void

0e%isiting Procedural0e%isiting Procedural


35/40

35

0e%isiting Procedural0e%isiting Procedural

ProgrammingProgramming #)) in P11@1 is taught as a procedural

progra!!ing language. In procedural progra!!ing, the idea is to design a

progra! to solve a proble! by concentrating on theprocedures :rst and data second. &his approach isknown as topdown design.

Procedures and data are 2 separate units that relatepri!arily via function para!eter.

)ain Program'ata

,unction1 ,unction2 ,unction3

bl i h d lP bl ith P d l


36/40

36

Problems +ith ProceduralProblems +ith Procedural

ProgrammingProgramming +nrestricted access to global

data and procedures. Poor !odeling of the real

world 5data and proceduresare separated6.

Got the way that hu!ansnaturally think about a situation.

Poor code reusability.

struct Student {

int id; vector subjects;};

void register_subject(Student? a){ $$$ }

void withdraw_subject(Student? s){ $$$ }

int "ain() {

Student s; register_subject (s); withdraw_subject (s);}

Wh Obj O i dWh Obj t O i t d


37/40

Wh* Object-OrientedWh* Object-Oriented

Programming?Programming?

%olve the problems of procedural programming. Lestrict access to data and procedures 5via

encapsulation6.

Better modeling of real world objects *via

abstraction+.4 ata and procedures are co!bined in a single unit.

# )asier to understand, correct, and modify.

Better code reusability # e!isting objects can be

reused to create new objects via inheritance *ecture

-+.

More useful for development of large and comple!

systems.


38/40

38

Con%erting ProceduralCon%erting Procedural

Program to OOPProgram to OOP

1. Identify the variables and the globalfunctions that use the variables aspara!eters, create a class and include thevariables and the global functions as class

!e!bers.2. ake all attributes private. #onst attributes

can opt for public.

A. For !ethods that use the class as

para!eter5s6, re!ove 0GD such para!eter. &hen update the !ethod body to refer to the!e!ber instead of the re!oved para!eter.

// 8rocedural version 8oint read8oint() {


39/40

39

// 8rocedural version2include using na"espace std;struct 8oint {

int @ y; // public by deault};

8oint read8oint();void print8oint (8oint);double dist8oint (8oint 8oint);

int "ain() { 8oint p- ' read8oint(); cout


40/40

40

// CC8 version2include using na"espace std;

class 8oint { int @ y; // private by deault public! void read8oint(); void print8oint(); double dist8oint (8oint A );

};

void 8oint!!read8oint() {cout > @ >> y;}

void 8oint!! print8oint() {cout

Lecture01 Objectorientedprogramming 130120010815 Phpapp01 (1)

Documents

Transcript of Lecture01 Objectorientedprogramming 130120010815 Phpapp01 (1)