в 14:21, 25 мая 2010

2010-05-25T14:21:17Z

Admin: 1 версия: Импорт контента...

2010-05-25T10:29:23Z

1 версия: Импорт контента...

Новая страница

==Use virtual functions and polymorphism.==

<source lang="cpp">#include <iostream>
#include <cstring>
using namespace std;

class Shape {
double width;
double height;

char name[20];
public:
Shape() {
width = height = 0.0;
strcpy(name, "unknown");
}

Shape(double w, double h, char *n) {
width = w;
height = h;
strcpy(name, n);
}

Shape(double x, char *n) {
width = height = x;
strcpy(name, n);
}

void display() {
cout << "Width and height are " << width << " and " << height << "\n";
}

double getWidth() { return width; }
double getHeight() { return height; }
void setWidth(double w) { width = w; }
void setHeight(double h) { height = h; }
char *getName() { return name; }

virtual double area() {
cout << "Error: area() must be overridden.\n";
return 0.0;
}

};

class Triangle : public Shape {
char style[20];
public:

Triangle() {
strcpy(style, "unknown");
}

Triangle(char *str, double w, double h) : Shape(w, h, "triangle") {
strcpy(style, str);
}

Triangle(double x) : Shape(x, "triangle") {
strcpy(style, "isosceles");
}

double area() {
return getWidth() * getHeight() / 2;
}

void showStyle() {
cout << "Triangle is " << style << "\n";
}
};

class Rectangle : public Shape {
public:

Rectangle(double w, double h) : Shape(w, h, "rectangle") { }

Rectangle(double x) : Shape(x, "rectangle") { }

bool isSquare() {
if(getWidth() == getHeight())
return true;
return false;
}

double area() {
return getWidth() * getHeight();
}
};

int main() {
Shape *shapes[5];

shapes[0] = &Triangle("right", 8.0, 12.0);
shapes[1] = &Rectangle(10);
shapes[2] = &Rectangle(10, 4);
shapes[3] = &Triangle(7.0);
shapes[4] = &Shape(10, 20, "generic");

for(int i=0; i < 5; i++) {
cout << "object is " << shapes[i]->getName() << "\n";
cout << "Area is " << shapes[i]->area() << "\n\n";
}

return 0;
}</source>
<pre class=codeResult>object is generic
Error: area() must be overridden.
Area is 0
object is generic
Error: area() must be overridden.
Area is 0
object is generic
Error: area() must be overridden.
Area is 0
object is generic
Error: area() must be overridden.
Area is 0
object is generic
Error: area() must be overridden.
Area is 0</pre>

← Предыдущая	Версия 14:21, 25 мая 2010
(нет различий)

C++ Tutorial/Class/polymorphism - История изменений

в 14:21, 25 мая 2010

Admin: 1 версия: Импорт контента...