从成员函数调用构造函数

问题来了:

定义一个名为Month的类，它是月份的抽象数据类型。您的类将有一个int类型的成员变量来表示月份(1代表1月，2代表2月，依此类推)。包括以下所有成员函数:构造函数设置月使用前三个字母的名称月三个参数,构造函数设置月使用一个整数作为参数(1 1月,2月2,等等),一个默认的构造函数,一个输入函数读取月一个整数,一个输入函数读取月的前三个字母的名称,一个输出函数,输出这个月为整数,一个输出函数，以月份名称的前三个字母输出月份，以及一个成员函数，以month类型的值返回下一个月份。在测试程序中嵌入你的类定义。

#include <iostream>
using namespace std;
class Month
{
public:
    Month (char letter1, char letter2, char letter3);
    Month (int numOfMonth);
    Month ();
    void inputAsNum(); // read month as integer
    void inputAsCh(); //  read first three chars of month
    void outputAsCh() const;
    void outputAsNum() const;
    Month nextMonth();
private:
    int month;
};
int main()
{
    Month test(5);
    //test.inputAsNum();
    cout << "Current month is " << endl;
    test.outputAsCh();
    test.outputAsNum();
    cout << endl;
    test.nextMonth();
    cout << "Next month is " <<endl;
    test.outputAsCh();
    test.outputAsNum();
    cout << endl;
    Month test2('a','p','r');
    //test2.inputAsCh();
    cout << "Current month is " << endl;
    test2.outputAsCh();
    test2.outputAsNum();
    cout << endl;
    test2.nextMonth();
    cout << "Next month is " <<endl;
    test2.outputAsCh();
    test2.outputAsNum();
    cout << endl;

    Month test3;
    test3.inputAsNum();
    cout << "Current month is " << endl;
    test3.outputAsCh();
    test3.outputAsNum();
    cout << endl;
    test3.nextMonth();
    cout << "Next month is " <<endl;
    test3.outputAsCh();
    test3.outputAsNum();
    cout << endl;
    Month test4;
    test4.inputAsCh();
    cout << "Current month is " << endl;
    test4.outputAsCh();
    test4.outputAsNum();
    cout << endl;
    test4.nextMonth();
    cout << "Next month is " <<endl;
    test4.outputAsCh();
    test4.outputAsNum();
    cout << endl;
    return 0;
}
Month::Month (char letter1, char letter2, char letter3)
{
    if ((letter1 == 'j')&&(letter2 == 'a')&&(letter3 == 'n'))
        month= 1;
    else if ((letter1 == 'f')&&(letter2 == 'e')&&(letter3 == 'b'))
        month= 2;
    else if ((letter1 == 'm')&&(letter2 == 'a')&&(letter3 == 'r'))
        month= 3;
    else if ((letter1 = 'a')&&(letter2 == 'p')&&(letter3 == 'r'))
        month= 4;
    else if ((letter1 == 'm')&&(letter2 == 'a')&&(letter3 == 'y'))
        month= 5;
    else if ((letter1 == 'j')&&(letter2 == 'u')&&(letter3 == 'n'))
        month= 6;
    else if ((letter1 == 'j')&&(letter2 == 'u')&&(letter3 == 'l'))
        month= 7;
    else if ((letter1 == 'a')&&(letter2 == 'u')&&(letter3 == 'g'))
        month= 8;
    else if ((letter1 == 's')&&(letter2 == 'e')&&(letter3 == 'p'))
        month= 9;
    else if ((letter1 == 'o')&&(letter2 == 'c')&&(letter3 == 't'))
        month= 10;
    else if ((letter1 == 'n')&&(letter2 == 'o')&&(letter3 == 'v'))
        month= 11;
    else if ((letter1 == 'd')&&(letter2 == 'e')&&(letter3 == 'c'))
        month= 12;
}
Month::Month (int numOfMonth)
                    :month(numOfMonth)
{ }
Month::Month ()
                    :month(1)
{ }
void Month::inputAsNum()
{
    int num;
    cout << "Enter num of month => ";
    cin  >> num;
    month = num;
}
void Month::inputAsCh()
{
    char c1,c2,c3;
    cout << "Enter three letters of month => ";
    cin  >> c1 >> c2 >> c3;
    Month::Month(c1,c2,c3);
}
void Month::outputAsCh() const
{
    if (month == 1)
        cout << "Jan ";
    else if (month == 2)
        cout << "Feb ";
    else if (month == 3)
        cout << "Mar ";
    else if (month == 4)
        cout << "Apr ";
    else if (month == 5)
        cout << "May ";
    else if (month == 6)
        cout << "Jun ";
    else if (month == 7)
        cout << "Jul ";
    else if (month == 8)
        cout << "Aug ";
    else if (month == 9)
        cout << "Sep ";
    else if (month == 10)
        cout << "Oct ";
    else if (month == 11)
        cout << "Nov ";
    else if (month == 12)
        cout << "Dec ";
}
void Month::outputAsNum() const
{
    cout << month;
}
Month Month::nextMonth()
{
    if (month < 12)
        month++;
    else if (month == 12)
        month = 1;
    return Month(month);
}

代码运行得很好。我尝试从成员函数void Month::inputAsCh()调用构造函数Month::Month (char letter1, char letter2, char letter3)。我可以通过改变Month::inputAsCh()的定义并将构造函数的定义复制粘贴到函数中来解决这个问题。但是，出于好奇，可以从成员函数调用构造函数吗?如果它是好的，Month::inputAsCh()工作错误，我也尝试Month test4变量。

Output                                  Expected Output
-------------                           -----------------
Current month is                        Current month is 
Nov 11                                  Nov 11
Next month is                           Next month is 
Dec 12                                  Dec 12
Current month is                        Current month is 
Apr 4                                   Apr 4
Next month is                           Next month is 
May 5                                   May 5
Enter num of month => 2                 Enter num of month => 2
Current month is                        Current month is 
Feb 2                                   Feb 2
Next month is                           Next month is 
Mar 3                                   Mar 3
Enter three letters of month => apr     Enter three letters of month => apr
Current month is                        Current month is 
Jan 1                                   Apr 4
Next month is                           Next month is 
Feb 2                                   May 5