C++复制控制

C/C++ code

class Person{protected:    string name;    char sex;    int age;public:    Person(void)    {        cout<<"In Person(void)"<<endl;    }    ~Person(void)    {        cout<<"In ~Person(void)"<<endl;    }    Person(string name, char sex, int age)    {        cout<<"In Person(string name, char sex, int age)"<<endl;        this->name = name;        this->sex = sex;        this->age = age;    }    virtual void printInfo(void)    {        cout<<"name:"<<name<<endl<<"age:"<<age<<endl;        cout<<"sex:";        if(sex == 0)        {            cout<<"Male";        }else        {            cout<<"Female";        }        cout<<endl;    }};class Employee:public Person{private:    int emp_num;    int salary;    string job;    public:    Employee(const Employee &e)    {        this->age = e.age + 10;        this->emp_num = this->emp_num + 2;        this->job = e.job;        this->name = e.name;        this->salary = e.salary;        this->sex = e.sex;        cout << "In Employee(const Employee &e)"<<endl;    }    Employee(void)    {        cout<<"In Employee(void)"<<endl;    }    ~Employee(void)    {        cout<<"In ~Employee"<<endl;    }    Employee(string name, char sex, int age, int emp_num, int salary, string job):Person(name, sex, age)    {        cout<<"In Employee(string name, char sex, int age, int emp_num, int salary, string job)"<<endl;        this->emp_num = emp_num;        this->salary = salary;        this->job = job;    }    void operator=(Employee e)    {        this->age = e.age + 3;        this->emp_num = this->emp_num + 1;        this->job = e.job;        this->name = e.name;        this->salary = e.salary;        this->sex = e.sex;        cout << "In Employee ="<<endl;    }    void printInfo(void)    {        cout<<"name:"<<name<<endl<<"age:"<<age<<endl;        cout<<"sex:";        if(sex == 0)        {            cout<<"Male";        }else        {            cout<<"Female";        }        cout<<endl<<"emp_num:"<<emp_num<<endl<<"salary:"<<salary<<endl<<"job:"<<job<<endl;    }};int _tmain(int argc, _TCHAR* argv[]){        Employee e_1("zhb", 0, 25, 20, 5000, "enigeer");    Employee e_2("pf", 0, 25, 1000, 2000, "unknown");        e_1 = e_2;        system("pause");    return 0;}

e_1 = e_2;这部分为什么会先后调用了复制构造函数和赋值运算符？e_1已经初始化过了，这里不是应该只调用赋值运算么？谢谢解答。

[解决办法]
void operator=(Employee e);
这种传参是按指传递，所以传参的时候会调用 复制构造函数。
改为
void operator=(Employee& e)就不会了。
而且一般都使用引用。