Question

下面是我要完成的“rhombus.cpp”文件的代码。但首先我要强调一下这个区域“Rhombus :: Rhombus（Vertex point，int radius）：Shape（point）{”..我的问题是在编译器中究竟发生了什么？：Shape（point）对我来说是全新的，所以我不确定该怎么做，特别是当我在int main中调用它时。如果我在//的评论下放置你的代码并添加评论等，那么我做了什么呢？非常感谢您的帮助！

#include "rhombus.h"

Rhombus::Rhombus(Vertex point, int radius) : Shape(point){
// constructs a Rhombus of radius around a point in 2D space
if((radius>centroid.getX()/2) || (radius>centroid.getX()/2))
{
    cout << "Object must fit on screen." << endl;
    system("pause");
    exit(0);
}
// place your code here and add comments that describe your understanding of        what is happening
this->radius = radius;
plotVertices();
}

int Rhombus::area()
{
// returns the area of a Rhombus
return 0;
}

int Rhombus::perimeter()
{
// returns the perimeter of a Rhombus
return 0;
}

void Rhombus::plotVertices()
{
// a formula for rotating a point around 0,0 is
// x' = x * cos(degrees in radians) - y * sin(degrees in radians)
// y' = y * cos(degrees in radians) + x * sin(degrees in radians)
// the coordinates for point A are the same as the centroid adjusted for the    radius
// the coordinates for point B are determined by rotating point A by 90 degrees
// the coordinates for point C are determined by rotating point A by 180 degrees
// the coordinates for point C are determined by rotating point A by 270 degrees
// remember that 0,0 is at the top left, not the bottom left, corner of the console

// place your code here and add comments that describe your understanding of what is happening
}

Rhombus.h

#include "shape.h"

class Rhombus : public Shape
{
int radius;

void plotVertices();
public:
Rhombus(Vertex point, int radius = 10);
int area();
int perimeter();
};

Shape.h

enter #pragma once
#include "console.h"
#include "vertex.h"
#include <iostream>
#include <list>
#include <cstdlib>
#include <cmath>
using namespace std;

#define PI 3.14159265358979323846

class Shape
{
list<Vertex>::iterator itr;
protected:
list<Vertex> vertices;
Vertex centroid;
void drawLine(int x1, int y1, int x2, int y2);
Shape(Vertex point);
double round(double x);
public:
void drawShape();
virtual int area() = 0;
virtual int perimeter() = 0;
virtual void outputStatistics();
void rotate(double degrees);
void scale(double factor);
};

Answer 1

这条线 Rhombus :: Rhombus（Vertex point，int radius）

是你班级的构造函数。它告诉您可以实例化/创建像

这样的Rhombus对象

int main(){
     Vertex v;
     Rhombus rhomb(v, 3);

此对象创建通常称为实例化。

额外的形状

 Rhombus::Rhombus(Vertex point, int radius): Shape(point)

描述如何创建Rhombus对象。即通过调用Shape中接受Vertex参数的构造函数。然后它运行构造函数中的其余代码。这是必要的，因为Rhombus继承了rhombus.h中的Shape。

您需要阅读的关键内容是继承。这很可能很早就被涵盖了。

需要一些帮助来澄清我试图完成C ++的一段代码

1 个答案: