c++ - 尝试使用 *this 引用已删除的函数

Question

我一直在为俄勒冈理工大学的 C++ 类(class)做一个项目，我遇到了一个错误，连我的教授都无法帮助我解决。我一直在尝试使用移动构造函数，但我不断收到错误提示:

function "Shapes::operator=(const Shapes &)" (declared implicitly) cannot be referenced -- it is a deleted function - line 31

'Shapes::operator=(const Shapes &)': attempting to reference a deleted function - line 31

// Shapes.h

#ifndef LAB1_SHAPES_H
#define LAB1_SHAPES_H

class Shapes {
protected:
    float m_width;
    float m_area;
    float m_perimeter;
public:
    Shapes() {
        m_width = 0;
        m_area = m_width * m_width;
        m_perimeter = 4 * m_width;
    }

    Shapes(float x) {
        if (x > 0) {
            m_width = x;
        }

        m_area = m_width * m_width;
        m_perimeter = 4 * m_width;
    }

    Shapes(Shapes&& move) noexcept {
        *this = move;
    }

    Shapes(const Shapes& copy) {
        m_width = copy.m_width;
        m_area = m_width * m_width;
        m_perimeter = 4 * m_width;
    }

    float getWidth() const {
        return m_width;
    }
    float getArea() const {
        return m_area;
    }
    float getPerimeter() const {
        return m_perimeter;
    }
};

#endif //LAB1_SHAPES_H

Answer 1

Shapes(Shapes&& move) noexcept

您为此类声明了一个移动构造函数。

这results in a deleted copy-assignment operator .这意味着默认情况下不提供给您:

An implicitly-declared copy assignment operator for class T is defined asdeleted if any of the following is true:

...

T has a user-declared move constructor; 

...

差不多就这些了。要解决这个问题，您需要定义自己的 operator= 重载，以实现此类拥有一个重载的任何意义。