在另一个C ++类中创建一个对象(Creating an object within another class C++)

在另一个C ++类中创建一个对象(Creating an object within another class C++)

我得到一个奇怪的运行时错误，我根本无法理解。 我正在创建我的类Circle的对象，它具有以下默认构造函数：

Circle::Circle() { this->radius = 0; this->center->setX(0); this->center->setY(0); }

正在初始化的变量是：

private: double radius; Point *center; };

当我尝试创建类圈的对象时，我收到运行时错误。 现在我只在动态声明Point对象时才会出现此错误。 我的语法有什么问题吗？ 当我在我的Circle类中声明Point时，改为：

Point center;

并将其初始化为：

Circle::Circle() { this->radius = 0; this->center.setX(0); this->center.setY(0); }

有用。 为什么在动态创建对象时会出现这些错误？ 我可以不像第一个例子中那样使用两个“ - >”吗？

这是我的第一篇文章，我希望这不是一个太愚蠢的问题。 提前致谢。

I'm getting a strange runtime error that I simply cannot comprehend. I'm making an object of my class Circle, which has the following default constructor:

Circle::Circle() { this->radius = 0; this->center->setX(0); this->center->setY(0); }

The variables that are being are initialized are:

private: double radius; Point *center; };

When I try to make an object of the class circle, I get a runtime error. Now I only get this error when the Point objectis declared dynamically. Is there anything wrong with my syntax? When I declare the Point in my Circle class like this instead:

Point center;

And initializes it like this instead:

Circle::Circle() { this->radius = 0; this->center.setX(0); this->center.setY(0); }

It works. Why do I get these errors when I create the object dynamically? Can I not use two "->" like in the first example?

This is my first post, I hope this is not a too stupid question. Thanks in advance.

最满意答案

你应该更好地使用

Circle { private: double radius; Point center; // <<<<<<< No pointer here };

你不需要指针。

当前代码的问题是没有为指针变量分配内存。 我也不建议这样做（例如使用center = new Point() ）。 如上所述，没有必要。

此外，您不需要此 - this->来访问类成员。 只需在构造函数中使用成员初始化列表：

Circle::Circle() : radius(0), center(0,0) { }

You should better use

Circle { private: double radius; Point center; // <<<<<<< No pointer here };

You don't need a pointer.

The problem with your current code is that no memory is allocated for your pointer variable. I'd also not recommend to do it (e.g. with center = new Point()). As mentioned, it's not necessary.

Also you don't need this-> to access class members. Just use the member initializer list in your constructor:

Circle::Circle() : radius(0), center(0,0) { }