使用公共和私有重载构造函数时的c ++垃圾成员值

Question

#include <iostream>

using namespace std;
class date{

    public:
        int month;
        int day;
        int year;

    private:
        date(int x, int y, int z);
    public:
        date(int x, int y);
};

date::date(int x, int y, int z): month{x}, day{y}, year{z} {

    cout << "Hello you called me PRIVATE constructor" << endl;

} 

date::date(int x, int y){
    cout << "Hello you called me PUBLIC constructor" << endl;
    date(x, y, 100);
}


int main(){

    date x{11, 21};

    cout << x.month << endl;
    cout << x.day << endl;
    cout << x.year << endl;

}

正如你在上面的代码中看到的,我有两个构造函数,在main中我用两个参数创建对象x.

这应该调用公共构造函数,后者又调用私有构造函数并初始化公共成员月份日和年份.

但是当我打印出会员价值时,我没有得到理想的结果.

Hello you called me PUBLIC constructor
Hello you called me PRIVATE constructor
392622664
1
0

而输出应该是:

Hello you called me PUBLIC constructor
Hello you called me PRIVATE constructor
11
21
100

我不知道我做错了什么.任何帮助将不胜感激.谢谢.

Answer 1

构造函数没有名称,也无法调用.该表达式date(x, y, 100);使用私有构造函数创建一个临时实例,该构造函数会立即销毁.您可以委派构造,但需要使用正确的构造函数委派语法.要委托构造函数,必须在初始化列表中执行此操作.它必须是初始化列表中的唯一元素.例如 :

#include <iostream>

using namespace std;
class date {

public:
    int month;
    int day;
    int year;

private:
    date(int x, int y, int z);
public:
    date(int x, int y);
};

date::date(int x, int y, int z) : month{ x }, day{ y }, year{ z } {

    cout << "Hello you called me PRIVATE constructor" << endl;

}

date::date(int x, int y) : date(x, y, 100) {
    cout << "Hello you called me PUBLIC constructor" << endl;
}


int main() {

    date x{ 11, 21 };

    cout << x.month << endl;
    cout << x.day << endl;
    cout << x.year << endl;
}