一、纯虚函数
纯虚函数不可实例化，且其派生类必须实例化。
#include<iostream>
#include"Shape.h"
#include"circle.h"
using std::cout;
using std::endl;
int main()
{
//Shape s{Color::black,true} 含有纯虚函数，不可以实例化
Circle c{
1.2,Color::green,false };
Shape* p = &c;
cout << p->getArea() << endl;
std::cin.get();
}
结果如上图所示。
二、相关文件
#include "Shape.h"
Shape::Shape(Color color_, bool filled_)
{
color = color_;
filled = filled_;
}
Color Shape::getColor() {
return color; }
void Shape::setColor(Color color_) {
color = color_; }
bool Shape::isFilled() {
return filled; }
void Shape::setFilled(bool filled_) {
filled = filled_; }
string Shape::toString()
{
std::array<string, 6> c{
"white"s,"black"s, "red"s, "green"s, "blue"s, "yellow"s, };
return "Shape : " + c[static_cast<int>(color)] + " " + (filled ? "filled"s : "not filled"s);
}
string Shape::colorTostring()
{
return colorNames[static_cast<int>(color)];
}
string Shape::filledToString()
{
return (filled ? "filled"s : "not filled"s);
}
#include"circle.h"
Circle::Circle()
{
radius = 1.0;
}
Circle::Circle(double radius_, Color color_, bool filled_) :Shape{
color_, filled_ }
{
radius = radius_;
}
double Circle::getArea()
{
return (3.14 * radius * radius);
}
double Circle::getRadius() const
{
return radius;
}
Circle& Circle::setRadius(double radius)
{
this->radius = radius;
return (*this);
}
string Circle::toString()
{
return ("Circle:radius" + std::to_string(radius) + "," + colorTostring() + " " + filledToString());
}
#pragma once
#include<iostream>
#include<string>
#include<array>
using std::string;
using namespace std::string_literals;
enum class Color
{
white,black,red,green,blue,yellow,
};
class Shape
{
private:
Color color{
Color::black };
bool filled{
false };
std::array<string, 6>colorNames{
"white"s,"blcak"s, "red"s, "green"s, "blue"s, "yellow"s, };
public:
Shape() = default;
Shape(Color color_, bool filled_);
Color getColor();
void setColor(Color color_);
bool isFilled();
void setFilled(bool filled_);
string filledToString();
string colorTostring();
string toString();
virtual double getArea() = 0; //注意:包含纯虚函数,就成为了抽象类.不可以实例化。同时，在其派生类中必须实例化。
};
#pragma once
#include"Shape.h"
class Circle:public Shape
{
private:
double radius;
public:
Circle();
Circle(double radius_, Color color_, bool filled_);
virtual double getArea() override;
public:
double getRadius() const;
Circle& setRadius(double radius);
string toString();
};