C++构造函数

 BIG THREE

#ifndef __Complex__
#define __Complex__
class Complex
{
public:
    Complex(double real = 0, double image = 0,const char * name = nullptr);
    virtual ~Complex();

    Complex(const Complex&com);
    Complex& operator=(const Complex &com);
    Complex& operator+=(const Complex &com);

    double Real()  const;
    double Image() const;
private:
    double _real;
    double _image;
    char * _name;
};
#endif

#include "Complex.h"
#include "string.h"
Complex::Complex(const double real, const double image, const char *name)
    :_real(real), _image(image)
{
    if (name)
    {
        size_t len = strlen(name) + 1;
        _name = new char[len];
        strcpy_s(_name, len, name);
    }
    else
    {
        _name = new char[1];
        *_name = '';
    }
}

Complex::~Complex()
{
    if (_name)
        delete[]_name;
    _name = nullptr;
}

Complex::Complex(const Complex & com)
{
    _real = com._real;
    _image = com._image;
    _name = nullptr;
    if (com._name)
    {
        size_t len = strlen(com._name) + 1;
        _name = new char[len];
        strcpy_s(_name, len, com._name);
    }

}

Complex & Complex::operator=(const Complex & com)
{
    _real = com._real;
    _image = com._image;

    if (this == &com)
        return *this;

    delete[] _name;
    _name = nullptr;

    if (com._name)
    {
        size_t len = strlen(com._name) + 1;
        _name = new char[len];
        strcpy_s(_name, len, com._name);
    }
    return *this;
}

Complex& Complex::operator+=(const Complex & com)
{
    _real += com._real;
    _image += com._image;
    return *this;
}

double Complex::Real() const
{
    return _real;
}

double Complex::Image() const
{
    return _image;
}

#include "Complex.h"
int main()
{
    Complex number = Complex(2, 1, "Hello");
    Complex number2(number);
    number2 = number;
    number = number;
    return 0;
}

注：

重载=赋值运算符时有两个要点：

1.   delete[] _name; _name = nullptr;   需要将原本的内存释放；
2.   if (this == &com) return *this; 　需要判断是否是自我赋值！