<< Chapter < Page Chapter >> Page >

Tuy nhiên, có thể sử dụng ép kiểu để chuyển đổi một con trỏ lớp cơ sở thành một con trỏ lớp dẫn xuất.

Ví dụ 5.1: Chương trình sau sẽ được chia thành nhiều file (gồm các file .H và .CPP) và tạo một project có tên là CT5_1.PRJ gồm các file .cpp

File POINT.H:

1: //POINT.H

2: //Định nghĩa lớp Point

3: #ifndef POINT_H

4: #define POINT_H

5:

6: class Point

7: {

8: protected:

9: float X,Y;

10: public:

11: Point(float A= 0, float B= 0);

12: void SetPoint(float A, float B);

13: float GetX() const

14: {

15: return X;

16: }

17: float GetY() const

18: {

19: return Y;

20: }

21: friend ostream&operator<<(ostream&Output, const Point&P);

22: };

23:

24: #endif

File POINT.CPP

1: //POINT.CPP

2: //Định nghĩa các hàm thành viên của lớp Point

3: #include<iostream.h>

4: #include "point.h"

5:

6: Point::Point(float A, float B)

7: {

8: SetPoint(A, B);

9: }

10:

11: void Point::SetPoint(float A, float B)

12: {

13: X = A;

14: Y = B;

15: }

16:

17: ostream&operator<<(ostream&Output, const Point&P)

18: {

19: Output<<'['<<P.X<<", "<<P.Y<<']';

20: return Output;

21: }

File CIRCLE.H

1: //CIRCLE.H

2: //Định nghĩa lớp Circle

3: #ifndef CIRCLE_H

4: #define CIRCLE_H

5:

6: #include "point.h"

7: class Circle : public Point

8: {

9: protected:

10: float Radius;

11: public:

12: Circle(float R = 0.0, float A = 0, float B = 0);

13: void SetRadius(float R);

14: float GetRadius() const;

15: float Area() const;

16: friend ostream&operator<<(ostream&Output, const Circle&C);

17: };

18:

19: #endif

File CIRCLE.CPP

1: //CIRCLE.CPP

2: //Định nghĩa các hàm thành viên của lớp Circle

3: #include<iostream.h>

4: #include<iomanip.h>

5: #include "circle.h"

6:

7: Circle::Circle(float R, float A, float B): Point(A, B)

8: {

9: Radius = R;

10: }

11:

12: void Circle::SetRadius(float R)

13: {

14: Radius = R;

15: }

16:

17: float Circle::GetRadius() const

18: {

19: return Radius;

20: }

21:

22: float Circle::Area() const

23: {

24: return 3.14159 * Radius * Radius;

25: }

26:

27: //Xuất một Circle theo dạng: Center = [x, y]; Radius = #.##

28: ostream&operator<<(ostream&Output, const Circle&C)

29: {

30: Output<<"Center = ["<<C.X<<", "<<C.Y

31:<<"]; Radius = "<<setiosflags(ios::showpoint)

32:<<setprecision(2)<<C.Radius;

33: return Output;

34: }

File CT5_1.CPP:

1: //CT5_1.CPP

2: //Chương trình 5.1: Ép các con trỏ lớp cơ sở tới các con trỏ lớp dẫn xuất

3: #include<iostream.h>

4: #include<iomanip.h>

5: #include "point.h"

6: #include "circle.h"

7:

8: int main()

9: {

10: Point *PointPtr, P(3.5, 5.3);

11: Circle *CirclePtr, C(2.7, 1.2, 8.9);

12: cout<<"Point P: "<<P<<endl<<"Circle C: "<<C<<endl;

13 //Xử lý một Circle như một Point (chỉ xem một phần lớp cơ sở)

14: PointPtr =&C;

15: cout<<endl<<"Circle C (via *PointPtr): "<<*PointPtr<<endl;

16 //Xử lý một Circle như một Circle

17: PointPtr =&C;

18: CirclePtr = (Circle *) PointPtr;

19: cout<<endl<<"Circle C (via *CirclePtr): "<<endl

20:           <<*CirclePtr<<endl<<"Area of C (via CirclePtr): "

21:           <<CirclePtr->Area()<<endl;

22: //Nguy hiểm: Xem một Point như một Circle

23: PointPtr =&P;

24: CirclePtr = (Circle *) PointPtr;

25: cout<<endl<<"Point P (via *CirclePtr): "<<endl

26:           <<*CirclePtr<<endl<<"Area of object CirclePtr points to: "

Questions & Answers

how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
can nanotechnology change the direction of the face of the world
Prasenjit Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Good
Got questions? Join the online conversation and get instant answers!
QuizOver.com Reply

Get the best Algebra and trigonometry course in your pocket!





Source:  OpenStax, Lập trình hướng đối tượng. OpenStax CNX. Jul 29, 2009 Download for free at http://cnx.org/content/col10794/1.1
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Lập trình hướng đối tượng' conversation and receive update notifications?

Ask