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K Chng thut lp trnh
Phn III: Lp trnh hng i tng Chng 5: Lp v i tng
0101010101010101100001 0101010101010101100001 StateController 0101010100101010100101 0101010100101010100101 1010011000110010010010 1010011000110010010010 start() 1100101100100010000010 1100101100100010000010 stop() 0101010101010101100001 0101010101010101100001 0101010100101010100101 0101010100101010100101 1010011000110010010010+ B*u; 1010011000110010010010 y = A*x 1100101100100010000010+ d*u; 1100101100100010000010 x = C*x LQGController 0101010101010101100001 0101010101010101100001 0101010100101010100101 0101010100101010100101 start() 1010011000110010010010 stop() 1010011000110010010010 1100101100100010000010 1100101100100010000010 9/15/2006
2004, HONG MINH SN
Ni dung chng 5
5.1 5.2 5.3 5.4 5.5 Khi nim T cu trc sang lp Bin thnh vin Hm thnh vin Kim sot truy nhp
2004, HONG MINH SN
Chng 5: Lp v i tng
2005 - HMS
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5.1 Khi nim
i tng l g? Thc th phn mm M hnh/i din ca mt i tng vt l:
-- -- -- -- Tank, Heater, Furnace Motor, Pump, Valve Sensor, Thermometer, Flowmeter Control Loop, Control System
Hoc mt i tng logic ("conceptual object):
2004, HONG MINH SN
-- Trend, Report, Button, Window -- Matrix, Vector, Polynomial
Chng 5: Lp v i tng
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Mt i tng c...
Hnh vi
Cc thuc tnh (attributes) Trng thi (state) D liu Quan h Hnh vi (behavior) Cc php ton c tnh phn ng
2004, HONG MINH SN
sa, cn, chy chy khi gp nguy him
Trng thi
t th sc khe
Thuc tnh Cn cc
Cn cc (identity) Ng ngha/trch nhim (semantic/responsibilities)
Tn: Rex ID: 007
mu lng: vng ging: Berge
Ng ngha
Ch gi nh
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Chng 5: Lp v i tng
Lp l g?
Mt lp l thc thi ca cc i tng c chung
-- -- -- -- Ng ngha Thuc tnh Quan h Hnh vi
Lp = ng gi [Cu trc d liu + hm thao tc]
-- Lp cc vector, lp cc ma trn (d liu phn t + cc php truy nhp v php ton c bn) -- Lp cc hnh ch nht (cc d liu ta + php v, xa,...) -- Lp cc m hnh hm truyn (cc h s a thc t/mu, cc php ton xc nh tnh n nh, xc nh cc im cc,...)
2004, HONG MINH SN
Cc d liu ca mt lp => bin thnh vin Cc hm ca mt lp => hm thnh vin Cc bin ca mt lp => mt i tng, mt th nghim
Chng 5: Lp v i tng
2005 - HMS
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Lp trnh hng i tng (object-oriented programming, OOP)
Tru tng ha (abstraction): gip n gin ha vn , d s dng li ng gi d liu/che du thng tin (data encapsulation/ information hiding): nng cao gi tr s dng li v tin cy ca phn mm Dn xut/tha k (subtyping/inheritance): gip d s dng li m phn mm v thit k a hnh/a x (polymorphism): gip phn nh trung thc th gii thc v nng cao tnh linh hot ca phn mm
2004, HONG MINH SN
Phng php lun hng i tng cho php t duy mc tru tng cao nhng gn vi th gii thc!
2005 - HMS
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Chng 5: Lp v i tng
5.2 T cu trc sang lp
struct Time { int hour; // gio int min; // phut int sec; // giay }; void addHour(Time& t, int h) { t.hour += h; } void addMin(Time& t, int m) { t.min += m; if (t.min > 59) { t.hour += t.min/60; t.min %= 60; } else if (t.min < 0) { t.hour += (t.min/60 - 1); t.min = (t.min % 60) + 60; } } void addSec(Time& t, int s) { t.sec += s; if (t.sec > 59) { addMin(t, t.sec/60); t.sec %= 60; } else if (t.sec < 0) { addMin(t, t.sec/60 - 1); t.sec = (t.sec % 60) + 60; } } void main() { Time t = {1, 0, 0}; addMin(t,60); addMin(t,-5); addSec(t,25); ... } 2005 - HMS
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2004, HONG MINH SN
Chng 5: Lp v i tng
Mt s vn ca cu trc
Truy nhp d liu trc tip, khng c kim sot c th dn n khng an ton
Time t1 = {1, 61, -3}; Time t2; int h = t2.hour; int m = 50; t2.min = m + 15; // ??! // Uncertain values // ??! // ??!
Khng phn bit gia "chi tit bn trong" v "giao din bn ngoi", mt thay i nh chi tit bn trong cng bt ngi s dng phi thay i m s dng theo! V d: cu trc Time c sa li tn bin thnh vin:
2004, HONG MINH SN
struct Time { int h, m, s; };
on m c s khng bin dch c:
Time t; t.hour = 5;
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Chng 5: Lp v i tng
ng gi hay "lp ha"
class Time { int hour; // gio int min; // phut int sec; // giay public: Time() {hour=min=sec=0;}
Bin thnh vin (member variable) Hm to (constructor)
void setTime(int h, int m, int s) { hour = h; min = sec = 0; addSec(s); addMin(m); }
2004, HONG MINH SN
int getHour() { return hour; } int getMin() { return min; } int getSec() { return sec; } void addHour(int h) { hour += h; } ...
Hm thnh vin (member functions)
Chng 5: Lp v i tng
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void addMin(int m) { min += m; if (min > 59) { hour += min/60; min %= 60; } else if (min < 0) { hour += (min/60 - 1); min = (min % 60) + 60; } } void addSec(int s) { sec += s; if (sec > 59) { addMin(sec/60); sec %= 60; else } if (sec < 0) { addMin(sec/60 - 1); sec = (sec % 60) + 60; } }
};
Chng 5: Lp v i tng 2005 - HMS
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2004, HONG MINH SN
void main() { Time t; t.addHour(1); t.addMin(60); t.addMin(-5); t.addSec(25); t.hour = 1; // error t.min = 65; // error t.sec = -3; // error t.setTime(1, 65, -3); int h = t.getHour(); int m = t.getMin(); int s = t.getSec(); }
5.3 Bin thnh vin
Khai bo bin thnh vin ca mt lp tng t nh cu trc
class Time { int hour, min, sec; ... };
Mc nh, cc bin thnh vin ca mt lp khng truy nhp c t bn ngoi (bin ring), ng nhin cng khng khi to c theo cch c in:
Time t = {1, 0, 0}; t.hour = 2;
2004, HONG MINH SN
// error! // error!
C th lm cho mt bin thnh vin truy nhp c t bn ngoi (bin cng cng), tuy nhin t khi c l do cn lm nh th:
class Point { public: int x,y; };
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Chng 5: Lp v i tng
Kim sot vic truy nhp cc bin ring thng qua cc hm thnh vin Cch duy nht khi to gi tr cho cc bin thnh vin l s dng hm to:
class Time { ... public: Time() {hour=min=sec=0;} }; Time t; // t.hour = t.min = t.sec = 0;
Mt s bin thnh vin c vai tr lu tr trng thi bn trong ca i tng, khng nn cho truy nhp t bn ngoi (ngay c gin tip qua cc hm)
2004, HONG MINH SN
class PID { double Kp, Ti, Td; double I; ... };
// controller parameters // internal state
Chng 5: Lp v i tng
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5.4 Hm thnh vin
nh ngha cu trc & hm
struct Time { int hour, min, sec }; void addHour(Time& t, int h) { t.hour += h; } ...
nh ngha lp
class Time { int hour,min,sec; public: void addHour(int h) { hour += h; } ... };
Gi hm vi bin cu trc
2004, HONG MINH SN
Gi hm thnh vin ca T
Time t; ... t.addHour(5);
Time t; ... addHour(t,5);
y c s khc nhau v cch vit, nhng cha c s khc nhau c bn
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Chng 5: Lp v i tng
Khai bo v nh ngha hm thnh vin
Thng thng, lp cng cc hm thnh vin c khai bo trong tp tin u (*.h). V d trong tp c tn "mytime.h":
class Time { int hour,min,sec; public: void addHour(int h); void addMin(int m); void addSec(int s); ... };
Cc hm thng c nh ngha trong tp tin ngun (*.cpp):
2004, HONG MINH SN
#include "mytime.h" ... void Time::addHour(int h) { hour += h; }
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Chng 5: Lp v i tng
C th nh ngha mt hm thnh vin trong tp tin u di dng mt hm inline (ch nn p dng vi hm n gin), v d:
inline void Time::addHour(int h) { hour += h;}
Mt hm thnh vin cng c th c nh ngha trong phn khai bo lp => mc nh tr thnh hm inline, v d
class Time { int hour,min,sec; public: void addHour(int h) { hour += h; } };
Khi nh ngha hm thnh vin, c th s dng cc bin thnh vin v gi hm thnh vin khc m khng cn (thm ch khng th c) a tn bin i tng, v d:
2004, HONG MINH SN
void Time::addSec(int s) { ... addMin(sec/60); ... }
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Chng 5: Lp v i tng
Bn cht ca hm thnh vin?
class Time { int hour,min,sec; public: Time() { hour=min=sec=0; } void addHour(int h) { this->hour += h;// con tr this chnh l a ch ca } // i tng gi hm thnh vin ... }; void main() { Time t1,t2; t1.addHour(5); t2 = t1; t2.addHour(5); ... }
2004, HONG MINH SN
// // // //
T ng gi hm to Time() cho t1 v t2 C th hiu nh l addHour(&t1,5); OK C th hiu nh l addHour(&t2,5);
Chng 5: Lp v i tng
2005 - HMS
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5.5 Kim sot truy nhp
public: Cc thnh vin cng cng, c th s dng c t bn ngoi private: Cc thnh vin ring, khng th truy nhp c t bn ngoi, ngay c trong lp dn xut (s cp sau)
class Time { private: int hour,min,sec; ... };
Mc nh, khi khai bo class th cc thnh vin l private.
2004, HONG MINH SN
protected: Cc thnh vin c bo v, khng th truy nhp c t bn ngoi, nhng truy nhp c cc lp dn xut (s cp sau)
Chng 5: Lp v i tng
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5.6 Con tr i tng
#include "mytime.h" void main() { Time t; // t.addHour(5); Time *pt = &t; // pt->addSec(70); pt = new Time; // pt->addMin(25); ... delete pt; pt = new Time[5]; // for (int i=0; i < 5; pt[i].addSec(10); ... delete [] pt; } call constructor Time() pt is identical to this pointer call constructor Time()
call constructor 5 times ++ i)
2004, HONG MINH SN
Chng 5: Lp v i tng
2005 - HMS
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Bi tp v nh
Da trn cu trc Vector v cc hm lin quan thc hin trong chng 4, hy xy dng lp i tng Vector vi cc hm thnh vin cn thit. Khai bo mt lp thc hin lu tr thng tin ca mt lp sinh vin gm nhng thnh phn thuc tnh nh sau:
-- S hiu sinh vin : Kiu s nguyn -- H v tn: Chui k t -- Nm sinh: Kiu s nguyn
Khai bo v nh ngha m rng lp qun l sinh vin bng cc hm thnh vin thc hin cc chc nng nh sau:
2004, HONG MINH SN
-- -- -- --
Nhp h tn sinh vin Nhp s hiu sinh vin Nhp nm sinh Tm v hin th thng tin sinh vin khi bit m s
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Chng 5: Lp v i tng