c++ - 如何在 C++ 中使用类修改器将变量加倍

Question

这是我的第一篇文章，如果我缺乏礼仪，请见谅。我正在尝试通过引用一个函数来传递一个 Rectangle 对象，然后使用类修改器将尺寸加倍。我没有语法错误，看来我只是错误地调用了 r.setWidth() 和 r.setHeight() 突变器。我认为这会起作用:r.setWidth(w * 2)，但它不起作用。任何帮助将非常感激。

#include <iostream>
#include "Rectangle.h"
using namespace std;

Rectangle::Rectangle() { width = 1; height = 1; }
Rectangle::Rectangle(int w, int h) { width = w; height = h; }
Rectangle::~Rectangle() {}
int Rectangle::getWidth() { return width; }
int Rectangle::getHeight() { return height; }
void Rectangle::setWidth(int w) { width = w; }
void Rectangle::setHeight(int h) { height = h; }
int Rectangle::calculateArea() { return width * height; }

// end of Rectangle class implementation

void displayRectangle(Rectangle r);
void doubleAndDisplayRectangle(Rectangle& r);

int main()
{
    Rectangle r1, r2;
    int w, h; // temp width and height

    cout << "Please enter the width and height for the first rectangle: ";
    cin >> w >> h;
    r1.setWidth(w);
    r1.setHeight(h);

    cout << "Please enter the width and height for the second rectangle: ";
    cin >> w >> h;
    r2.setWidth(w);
    r2.setHeight(h);

    displayRectangle(r1);
    displayRectangle(r2);

    doubleAndDisplayRectangle(r1);
    doubleAndDisplayRectangle(r2);

    return 0;
}

void displayRectangle(Rectangle r)
{
    int w, h, area;
    cout << "Rectangle width = " << r.getWidth() << ", height = " << r.getHeight() << ", and area = " << r.calculateArea() << endl;
}

void doubleAndDisplayRectangle(Rectangle& r)
{
    int w, h, area;
    cout << "Doubling the rectangle dimensions!" << endl;
    /*r.setWidth(w)
    r.setHeight(h)*/
    cout << "Rectangle width = " << r.getWidth() << ", height = " << r.getHeight() << ", and area = " << r.calculateArea() << endl;
}

如果需要的话，这是我的 h 文件。

#ifndef _RECTANGLE_H
#define _RECTANGLE_H

// declare the Rectangle class
class Rectangle
{
    private:
        int width = 0, height = 0;
    public:
        Rectangle();
        Rectangle(int w, int h);
        ~Rectangle();
        int getWidth();
        int getHeight();
        void setWidth(int w);
        void setHeight(int h);
        int calculateArea();
};

#endif

Answer 1

如果你想将它的当前值加倍，那么你需要使用你的getters 来获取该值，这样你就可以将它加倍。

像这样:

void doubleAndDisplayRectangle(Rectangle& r)
{
    cout << "Doubling the rectangle dimensions!" << endl;

    int current_width = r.getWidth(); // get current width

    r.setWidth(current_width * 2); // set it to double

    int current_height = r.getHeight(); // get current height

    r.setHeight(current_height * 2); // set it to double

    cout << "Rectangle width = " << r.getWidth() << ", height = " << r.getHeight() << ", and area = " << r.calculateArea() << endl;
}