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Lagunov
Asked:2022-05-27 13:23:08 +0000 UTC2022-05-27 13:23:08 +0000 UTC

如何使用类实例创建和填充数组？

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我正在用 C++ 编程并使用 SFML 图形库。

#include <SFML/Graphics.hpp>
using namespace sf;
using namespace std;

class Ball //Класс шара
{
public:
    Ball(double radius, Color color, double x, double y, double dx, double dy) //dy и dx - направления шара
    {
        this->radius = radius;
        this->color = color;
        this->x = x;
        this->y = y;
        this->dx = dx;
        this->dy = dy;
    }

    void draw(RenderWindow& window, CircleShape& shape) //Рисуем шар
    {
        shape.setFillColor(this->color);
        shape.setRadius(this->radius);
        shape.setOrigin(this->radius, this->radius);
        shape.setPosition(this->x, this->y);
        window.draw(shape);
    }

    void move(int winSize) //Двигаем шар
    {
        this->x += this->dx;
        this->y += this->dy;

        if (this->y < this->radius)
        {
            this->dy = -this->dy;
            this->y = this->radius;
        }
        else if (this->y > winSize - this->radius)
        {
            this->dy = -this->dy;
            this->y = winSize - this->radius;
        }

        if (this->x < this->radius)
        {
            this->dx = -this->dx;
            this->x = this->radius;
        }
        else if (this->x > winSize - this->radius)
        {
            this->dx = -this->dx;
            this->x = winSize - this->radius;
        }
    }

    void update(RenderWindow& window, CircleShape& shape, int winSize) //Сначала двигаем шар, а потом рисуем
    {
        this->move(winSize);
        this->draw(window, shape);
    }

private:
    double radius;
    Color color;
    double y;
    double x;
    double dy;
    double dx;
};

int main()
{
    const int winSize = 900;
    RenderWindow window(VideoMode(winSize, winSize), "Ball"); //Окно
    CircleShape shape(0);
    Ball ball(30, Color(255, 255, 0), 300, 450, 3, 2); //Шар

    while (window.isOpen())
    {
        Event event;
        while (window.pollEvent(event)) //Проверка событий
        {
            switch (event.type)
            {
                case Event::Closed:
                    window.close();
                    break;

                default:
                    break;
            }
        }

        window.clear();
        ball.update(window, shape, winSize); //Двигаем и рисуем шар
        window.display();
    }
}

一个Ball ball(30, Color(255, 255, 0), 300, 450, 3, 2);球被创建并在它的帮助ball.update(window, shape, winSize);下移动并显示在屏幕上。但是如果我想创造更多像 100 这样的球怎么办？您可以创建一个数组balls，指定其大小const int numberOfBalls并用球填充它，然后ball.update(window, shape, winSize);将其替换为

for (int i = 0; i < numberOfBalls; i++)
    {
        balls[i].update(window, shape, winSize);
    }

为每个球调用函数update()。但我不能用球填充阵列。我试图用这样的球创建和填充一个数组

const int numberOfBalls = 100;
Ball balls[numberOfBalls];
for (int i = 0; i < numberOfBalls; i++)
{
    balls[i] = ball(30, Color(255, 255, 0), 300, 450, 3, 2);
}

但是visual studio说有2个错误。第一个是Ball balls[numberOfBalls];没有默认构造函数，第二个是没有定义balls[i] = ball(30, Color(255, 255, 0), 300, 450, 3, 2);标识符。ball

c++

1 个回答

  1. Best Answer

    如果使用数组不重要，我建议std::vector. 使用它，您可以像这样转换代码：

    #include <vector>
//...
//...
//...
const int numberOfBalls = 100;
std::vector<Ball> balls;
for (int i = 0; i < numberOfBalls; i++)
{
    // Обратите внимание, как уже заметили в комментариях, имя класса с заглавной буквы
    balls.push_back(Ball(30, Color(255, 255, 0), 300, 450, 3, 2));
}

    此外，可以以与常规数组的元素相同的方式访问向量的元素：

    for (int i = 0; i < numberOfBalls; i++)
{
    balls[i].update(window, shape, winSize);
}

    它可以更方便，但这里已经阅读了有关向量的信息

    • 1

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