How to properly overload >> input operator?

[MisterTams]

I am trying to overload the >> operator. I want to use my object called testcase1 and initialize it with the overloaded >> operator to set the month number (1-12).
The << operator works fine. Just need help with the >> operator.

.cpp

#include <iostream>
#include <string>
#include "Month.h"
using namespace std;

int main ()
{
	//int choice;
	//int monthnum;
	string Monthname;
	string Months[12] = { "January", "February", "March", "April", "May", "June", "July",
		"August", "September", "October", "November", "December" };

	int numOfMonth[12] = { 1,2,3,4,5,6,7,8,9,10,11,12 };

	Month testcase1;

	cout << "Please enter a number (1-12) to initialize the month object" << endl;
	cin >> testcase1;

	cout << testcase1;

	/*while (monthnum < 0 || monthnum > 12)
	{
		cout << "Invalid choice. Please enter a month (1-12) only!" << endl;
		cin.clear();
		cin.ignore();
		cin >> monthnum;
	}*/

	return 0;
}

*BELOW*
Look at line 127, am I doing this right?

.h

#ifndef Month_h
#define Month_h
#include <string>
#include <iostream>
using namespace std;

class Month
{
private:
	int monthNumber;
	string name;
public:

	string Months[12] = { "January", "February", "March", "April", "May", "June", "July",
	"August", "September", "October", "November", "December"};

	int numOfMonth[12] = {1,2,3,4,5,6,7,8,9,10,11,12};

	//default constructor
	Month()
	{
		monthNumber = 1;
		name = "January";
	}

	Month(string monthName)
	{
		for (int x = 0; x < 12; x++)
		{
			if (Months[x] == monthName)
			{
				name = Months[x];
				monthNumber = numOfMonth[x];
				break;
			}
		}
	}

	Month(int MonthNUM)
	{
		monthNumber = numOfMonth[MonthNUM - 1];
		name = Months[MonthNUM - 1];
	}

	void setName(string monthName)
	{
		for (int x = 0; x < 12; x++)
		{
			if (Months[x] == monthName)
			{
				name = Months[x];
				monthNumber = numOfMonth[x];
				break;
			}
		}
	}

	void setMonthNumber(int MonthNUM)
	{
		monthNumber = numOfMonth[MonthNUM - 1];
		name = Months[MonthNUM - 1];

		if (MonthNUM > 12)
		{
			monthNumber = numOfMonth[0];
			name = Months[0];
		}

		if (MonthNUM < 1)
		{
			monthNumber = numOfMonth[11];
			name = Months[11];
		}
	}

	int getMonthNum()
	{
		return monthNumber;
	}

	string getMonthName()
	{
		return name;
	}

	// overloaded ++ postfix operator function
		Month operator ++ (int) //dummy parameter, because of this, C++ will know this is postfix mode
	{
		Month temp;
		monthNumber++;
		setMonthNumber(monthNumber);
		return temp;
	}

	Month operator ++ () //prefix mode
	{
		Month temp;
		++monthNumber;
		setMonthNumber(monthNumber);
		return *this;
	}

	// overloaded ++ postfix operator function
	Month operator -- (int) //dummy parameter, because of this, C++ will know this is postfix mode
	{
		Month temp;
		monthNumber--;
		setMonthNumber(monthNumber);
		return temp;
	}

	Month operator -- () //prefix mode
	{
		Month temp;
		--monthNumber;
		setMonthNumber(monthNumber);
		return *this;
	}
	
	friend ostream &operator << (ostream &out, Month temp) //overloaded << (output) operator
	{
		out << "Month : " << temp.getMonthNum() << endl;
		out << "Month : " << temp.getMonthName() << endl;
		return out;
	}

	friend istream &operator >> (istream &in, Month temp) //overloaded >> (input) operator
	{
		int mnth;
		cout << "Enter Month Number: ";
		in >> mnth;
		return in;
	}

};
#endif // !Month_h

[coder777]

Look at line 127, am I doing this right?

No, you pass the object by value, i.e. a copy of the object. You should pass it by reference plus you should modify the passed object, instead you feed a local variable which is lost when the operator is done.

[MisterTams]

coder777,

Ok so how exactly can I return it?

I cannot figure it out for the life of me..
Here is what I have as of right now...

	friend istream &operator >> (istream &in, Month &temp) //overloaded >> (input) operator
	{
		int mnth;
		cout << "Enter Month Number: ";
		in >> mnth;
		return temp.setMonthNumber(mnth);
	}

[48T7M4Gy]

return in;

[MisterTams]

kemort,

I did return in originally...

Similar to the code as I had in the original post. It didn't do what I intended. Once I used cout with the object in main, it defaulted to Setting the number as 1 and the month as January. Sad!

- MisterTams

[48T7M4Gy]

Well, I haven't looked all that closely at the rest of your code. I concentrated on the return problem which solves that part AFAICS.

An observation on your months though. The index value of Months array (even the [12]) makes the numOfMonth array redundant.
string Months[] = { "dummy","January", "February", "March", "April", "May", "June", "July","August", "September", "October", "November", "December"}; is all that's required and everything follows from that.

[48T7M4Gy]

Something to consider. Remove the redundant information being recorded by the data abstraction of a month being simple the month number.

using namespace std;

static const string Months[] =
{
    "dummy", "January", "February", "March", "April", "May", "June",
    "July", "August", "September", "October", "November", "December"
};

class Month
{
private:
    int monthNumber;

public:
    Month(){monthNumber = 1;}
    
    Month(string monthName){
        for (int x = 1; x <= 12; x++){ // oops!
            if (Months[x] == monthName){monthNumber = x;
            }
        }
    }
    
    Month(int MonthNUM){monthNumber = MonthNUM;}
    
    void setMonthNumber(string month_name){
        for (int x = 0; x < 12; x++){
            if (Months[x] == month_name){
                monthNumber = x;
            }
        }
    }
    
    int getMonthNum(){return monthNumber;}
    
    string getMonthName(){return Months[monthNumber];}
    
    friend ostream &operator << (ostream &out, Month temp){
        out
        << "Month : " << temp.getMonthNum() << ' '
        << "Month : " << temp.getMonthName() << endl;
        return out;
    }
    
    friend istream &operator >> (istream &in, Month &month){
        cout << "Enter month no: ";
        in >> month.monthNumber;
        return in;
    }
};

int main (){
    Month testcase1;
    cin >> testcase1;
    
    cout << testcase1.getMonthName() << '\n';
    cout << testcase1 << '\n';
    
    return 0;
}

Enter month no: 7
July
Month : 7 Month : July

Program ended with exit code: 0

[coder777]

Change the operator>> to:

	friend istream &operator >> (istream &in, Month temp) //overloaded >> (input) operator
	{
		int mnth;
		cout << "Enter Month Number: ";
		in >> monthNumbermnth;
		return in;
	}

Note that the operator<< does not match, hence writing to a file and reading from the same file will show the wrong results. A matching operator<< would be this:

	friend ostream &operator << (ostream &out, Month temp) //overloaded << (output) operator
	{
		out << "Month : " << temp.getMonthNum() << endl;
		out << "Month : " << temp.getMonthName() << endl;
		out << monthNumber << endl;
		return out;
	}

You can remove the member variable name as kemort hinted because you can obtain the names from the Months array.

Regarding the numOfMonth array: I would think you misunderstood the use of it. I would think that it contains the number of days of the month. I.e. int numOfMonth[12] = {31,28,31,...};

[48T7M4Gy]

The possible misunderstanding of the numOfMonth array and 'repair' makes sense to me.

As a small embellishment two points:
1. [12] - the 12 again is redundant.
2. make the zero-th element -1 or 99 so that month[1] is directly/intuitively/conventionally mapped to "January", [12] to "December".

[MisterTams]

kemort and coder777,

You guys helped tremendously. It is a lot clearer to me now.
Thank you so very much!