Chuong 02 - Tong Quan Ve Lap Trinh Huong Doi Tuong

TNG QUAN V LP TRNH HNG I

TNG

ThS. Trn Anh Dng

Ni dung

14/09/2014 Lp trnh hng i tng 2

Gii thiu 1

Cc phng php lp trnh 2

Mt s khi nim c bn 3

Cc c im quan trng ca OOP 4

Mt s thut ng OOP 5 5

Gii thiu

Mc tiu ca k s lp trnh:

To ra sn phm tt mt cch c hiu qu

Nm bt c cng ngh


Gii thiu

phc tp v ln ngy cng cao:

Mt s h Unix cha khong 4M dng lnh

MS Windows cha hng chc triu dng lnh

Ngi dng ngy cng i hi nhiu chc

nng, c bit l chc nng thng minh

Phn mm lun cn c sa i


Gii php

Cn kim sot chi ph:

Chi ph pht trin

Chi ph bo tr

Gii php chnh l s dng li (ti s

dng):

Gim chi ph v thi gian pht trin

Nng cao cht lng


Gii php

s dng li (m ngun):

Cn d hiu

c coi l chnh xc

C giao din r rng

Tnh module ha

Khng yu cu thay i khi s dng trong

chng trnh mi


Mc tiu ca vic thit k mt phn mm

Tnh ti s dng (reusability): thit k cc

thnh phn c th c s dng trong

nhiu phn mm khc nhau

Tnh m rng (extensibility)

Tnh mm do (flexibility):

C th d dng thay i khi thm mi d liu

hay tnh nng.

Cc thay i khng lm nh hng nhiu n

ton b h thng


Cc phng php lp trnh

S tin ha ca cc phng php lp

trnh:

Lp trnh khng c cu trc

Lp trnh c cu trc (lp trnh th tc), hng

chc nng

Lp trnh hng i tng



L phng php xut hin u tin:

Cc ngn ng nh Assembly, Basic

S dng cc bin ton cc

Lm dng lnh GOTO

Nhc im?

Kh hiu, kh bo tr, hu nh khng th s dng li

Cht lng km, Chi ph cao

Khng th pht trin cc ng dng ln



V d:

10 k =1

20 gosub 100

30 if y > 120 goto 60

40 k = k+1

50 goto 20

60 print k, y

70 stop

100 y = 3*k*k + 7*k-3

110 return


Lp trnh c cu trc

T chc thnh cc chng trnh con (hay cc

module)

Mi chng trnh con m nhn x l mt cng

vic nh hay mt nhm cng vic trong ton b

h thng.

Mi chng trnh con ny li c th chia nh

thnh cc chng trnh con nh hn.


Chng trnh = Cu trc d liu + Gii thut

Lp trnh c cu trc

S dng cc lnh c cu trc: for, do, while, if

then else...

Cc ngn ng: Pascal, C,...

Chng trnh l tp cc hm/th tc

u im?

Chng trnh c module ha, do d hiu, d bo

tr hn

D dng to ra cc th vin phn mm


Lp trnh c cu trc

V d:

struct Date {

int year, mon, day;

};

//...

void print_date(Date d) {

printf(%d / %d / %d\n, d.day, d.mon, d.year);

}


Lp trnh c cu trc

Nhc im?

D liu v m x l l tch ri

Ngi lp trnh phi bit cu trc d liu

Khi thay i cu trc d liu thut ton phi thay i

theo

Kh m bo tnh ng n ca d liu

Khng t ng khi to hay gii phng d liu ng

Khng m t c y , trung thc h thng trong

thc t


Lp trnh hng i tng

Trong th gii thc, chung quanh chng ta l

nhng i tng, l cc thc th c mi quan

h vi nhau.

V d: Cc phng trong mt cng ty

Lp trnh hng i tng (Object Oriented

Programming LTHT)?

L phng php lp trnh ly i tng lm nn tng

xy dng thut gii, xy dng chng trnh.


Lp trnh Hng i tng


Lp trnh hng i tng l phng php

lp trnh da trn kin trc lp (class)

v i tng (object)

Mt s khi nim c bn

i tng (object)

Lp (class)


Mt s khi nim c bn

i tng (object):

Trong th gii thc, i tng c hiu nh l mt

thc th: ngi, vt hoc mt bng d liu

Mi i tng s tn ti trong mt h thng v c

ngha nht nh trong h thng.

i tng gip biu din tt hn th gii thc trn

my tnh

Mi i tng bao gm 2 thnh phn: thuc tnh v

thao tc (hnh ng).


Mt s khi nim c bn

V d i tng: mt ngi

Mt ngi c cc thuc tnh: tn, tui, a ch,

mu mt

Cc hnh ng: i, ni, th


Mt i tng l 1 thc th bao gm thuc tnh v hnh ng

Mt s khi nim c bn

Lp (class):

Cc i tng c cc c tnh tng t nhau c

gom chung thnh lp i tng. Mt lp i tng

c trng bng cc thuc tnh, v cc hnh ng

(hnh vi, thao tc).

Thuc tnh (Attribute): Mt thnh phn ca i tng,

c gi tr nht nh cho mi i tng ti mi thi im

trong h thng.

Thao tc (Operation): Th hin hnh vi ca mt i

tng tc ng qua li vi cc i tng khc hoc

vi chnh n. 14/09/2014 Lp trnh hng i tng 20

Mt s khi nim c bn

Mi thao tc trn mt lp i tng c th tng

ng vi mt ci t c th khc nhau. Mt ci t

nh vy c gi l mt phng thc (method).

Cng mt phng thc c th c p dng cho

nhiu lp i tng khc nhau, mt thao tc nh

vy c gi l c tnh a hnh (polymorphism).

Mt i tng c th thuc mt lp c gi l

mt th hin (instance) ca lp .


Interacting Objects


Class A Class B

Private:

data members

Private:

data members

Member methods Member methods

Constructor

Other

public methods

Public:

Destructor

Constructor

Other

public methods

Public:

DestructorMessage passing

Private:

methods

Private:

methods

S i tng

Ta dng s i tng m t cc lp i

tng. S i tng bao gm s lp v

s th hin.

S lp m t cc lp i tng trong h

thng, mt lp i tng c din t bng

mt hnh ch nht gm 3 phn:

Phn u ch tn lp

Phn 2 m t cc thuc tnh

Phn 3 m t cc thao tc ca cc i tng trong lp


S lp v s th hin


Sinh vien

Ho ten

Nam sinh

Ma so

iem TB

i hoc

i thi

Phan loai

(Sinh vien)

Nguyen Van A

1984

0610234T

9.2

Ten lp

Thuoc tnh

Thao tac

S o lp S o the hien

i tng = D liu + Phng thc

Thit k theo hng i tng

Tru tng ha d liu v cc hm/th tc

lin quan.

Chia h thng ra thnh cc lp/i tng.

Mi lp/i tng c cc tnh nng v

hnh ng chuyn bit.

Cc lp c th c s dng to ra

nhiu i tng c th.


Cc c im quan trng ca OOP


Cc lp i tng - Classes

ng gi - Encapsulation

Tha k - Inheritance

a hnh - Polymorphism

Tru tng ha


Thc th

Thuc tnh

Hnh ng

Th gii thc Tru tng ha Phn mm

D liu

hm

Tru tng ha

Cch nhn khi qut ha v mt tp cc i

tng c chung cc c im c quan tm (v

b qua nhng chi tit khng cn thit).


ng gi Che du thng tin


ng gi: Nhm nhng g c lin quan vi

nhau vo lm mt, sau ny c th dng

mt ci tn gi n

Cc hm/ th tc ng gi

cc cu lnh

Cc i tng ng gi

d liu ca chng v

cc th tc c lin quan

ng gi Che du thng tin

Che du thng tin: ng gi che mt s

thng tin v chi tit ci t ni b bn

ngoi khng nhn thy

Che giu nhng g m ngi dng khng cn.

Che giu nhng g m mnh cn gi b mt.


Tha k

L c ch cho php mt lp D c c cc thuc

tnh v thao tc ca lp C, nh th cc thuc tnh

v thao tc c nh ngha ti lp D.

Cho php ci t nhiu quan h gia cc i

tng:

c bit ha (l)

Khi qut ha


a hnh

L c ch cho php mt tn thao tc hoc

thuc tnh c th c nh ngha ti nhiu

lp v c th c nhiu ci t khc nhau ti

mi lp trong cc lp .


Cc u im ca OOP

Nguyn l k tha: trnh lp, ti s dng.

Nguyn l ng gi che du thng tin:

chng trnh an ton khng b thay i bi

nhng on chng trnh khc

D m rng, nng cp

M phng th gii thc tt hn.


Cc c tnh chnh ca OOP

Chng trnh c chia thnh cc i

tng.

Cc cu trc d liu c thit k sao cho

c t c i tng.

Cc hm thao tc trn cc vng d liu

ca i tng c gn vi cu trc d

liu .


Cc c tnh chnh ca OOP

D liu c ng gi li, c che giu v

khng cho php cc hm ngoi lai truy nhp

t do.

Cc i tng tc ng v trao i thng tin

vi nhau qua cc hm.

C th d dng b sung d liu v cc hm

mi vo i tng no khi cn thit.

Chng trnh c thit k theo cch tip cn

t di ln (bottom-up).


Mt s thut ng OOP

OOM (Object Oriented Methodology): Phng

php lun hng i tng

OOA (Object Oriented Analysis): Phn tch hng i tng.

OOD: Object Oriented Design (Thit k hng i tng).

OOP: Object Oriented Programming (LTHT).

Inheritance: K tha

Polymorphism: a hnh

Encapsulation: Tnh ng gi.


Ngn ng OOP

Cung cp c nhng kh nng lp trnh

hng i tng.

Cung cp kh nng kim sot truy cp

K tha

a hnh


Bi kim tra 1

Vit chng trnh cho php nhp mt

dy phn s. Ci t hm tnh tng

cc phn s v tm phn s ln nht.


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