c++传递指针

Question

在掌握指针方面仍然有很多问题，我试着不使用它们，但我不确定如何最好地完成以下内容。

我有两个类 Point 和 Ray，我也确信在某处可能已经有一个点类的实现，我应该改用它。所以我有这两个类，我正在尝试创建一个射线，并最终将其传递给其他东西，但我收到一个错误:Thread: EXC_BAD_ACCESS (code=1, address=0x0 )` 当我按照我正在做的方式创建光线并尝试访问它时。

class Point {
    public:
    float x;
    float y;
    Point();
    Point(float x, float y);
    ~Point();
};

Point::Point() {
    x = 0;
    y = 0;
}

Point::Point(float xPos, float yPos) {
    x = xPos;
    y = yPos;
    std::cout << "point created at: " << x << ", " << y << std::endl;
}

Point::~Point() {
    std::cout << "point destroyed" << std::endl;
}

class Ray {
public:

    std::unique_ptr<Point> origin;

    float angleInRadians;
    float length;

    float slope();
    Point* pointAtDistance(float percentage);
    Point* pointAtYPos(float yPos);

    Ray(Point& origin, float angleInRadians, float length);
    ~Ray();
};

Ray::Ray(Point& origin, float angleInRadians, float length) {
    origin = std::move(origin);
    angleInRadians = angleInRadians;
    length = length;
}

float Ray::slope() {
    return tanf(angleInRadians);
}

Point* Ray::pointAtDistance(float percentage) {
    return new Point(origin->x + (length * percentage) * cosf(angleInRadians), origin->y + (length * percentage) * sinf(angleInRadians));
}

Point* Ray::pointAtYPos(float yPos) {
    float B = origin->y - (slope() * origin->x);
    return new Point((yPos - B) / slope(), yPos);
}

Ray::~Ray() {
    std::cout << "point released" << std::endl;
    origin.release();
    std::cout << "ray destroyed" << std::endl;
}

第三行是出错的地方。

std::unique_ptr<Point> point(new Point(x,y));
std::unique_ptr<Ray> ray(new Ray(*point, M_PI/4, 100));
std::cout << "RAY origin: " << ray->origin->x << ", " << ray->origin->y << std::endl;

Answer 1

我相信这应该可行——我只是从字面上从您的代码中删除了所有指针并使用了实例。以您的 C++ 知识水平，指针几乎总是不必要的。

class Point {
    public:
        Point();
        Point(float x, float y);
        ~Point();

        float x;
        float y;
};

Point::Point() {
    x = 0;
    y = 0;
}

Point::Point(float xPos, float yPos) : x(xPos), y(yPos) {
    std::cout << "point created at: " << x << ", " << y << std::endl;
}

Point::~Point() {
    std::cout << "point destroyed" << std::endl;
}

class Ray {
    public:
        Ray(const Point& origin, float angleInRadians, float length);
        ~Ray();

        float slope();
        Point pointAtDistance(float percentage);
        Point pointAtYPos(float yPos);

        Point origin;

        float angleInRadians;
        float length;
};

Ray::Ray(const Point& o, float a, float l) : origin(o), angleInRadians(a), length(l) {
}

float Ray::slope() {
    return tanf(angleInRadians);
}

Point Ray::pointAtDistance(float percentage) {
    return Point(origin.x + (length * percentage) * cosf(angleInRadians), origin.y + (length * percentage) * sinf(angleInRadians));
}

Point Ray::pointAtYPos(float yPos) {
    float B = origin.y - (slope() * origin.x);
    return Point((yPos - B) / slope(), yPos);
}

Ray::~Ray() {
    std::cout << "ray destroyed" << std::endl;
}

希望这能让您入门。祝你完成剩下的作业!