C++学习日志37------纯虚函数

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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
#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
#include
#include
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();
};