Thread: Newbie overloading << operator (have searched, been good, but...)

Hi,

Firstly, many thanks in advance for any help or advice, it is very much appreciated.

I am trying to overload the << operator to output the data members 'loan' and 'name' for my student class.

Here is my setup (i have kept it very, very simple, in hope of a clear response). It might seem like a lot, but it is just 2 set methods and two get methods.

Code:

using namespace std;

Student::Student()
{
        loan = 0;
	name = "";
}

Student::Student(int extra)
{
	loan = extra;
	name = "";
}

void Student::setLoan(int amount)
{
	loan += amount;
}

void Student::setName(string word)
{
	name = word;
}

int Student::getLoan()
{
	return loan;
}

string Student::getName()
{
	return name;
}

Student::operator<< (ostream &out, Student)
{
	Student studentn;
	out << studentn.getName();
	out << studentn.getLoan();

	return studentn;
}

Here is my header file:

Code:

class Student
{
	private:
		int loan;
		string name;

	public:
		Student();
		Student(int);
		void setLoan(int);
		int getLoan();
		void setName(string);
		string getName();
		Student operator<< (ostream &out, Student);
};

This is my main function:

Code:

void main()
{

	int tmpLoan = 300;
	string tmpName = "Bruno";

	Student bruno (100);

	bruno.setLoan(tmpLoan);
	bruno.setName(tmpName);

	//cout << bruno.getLoan() << endl;
	//cout << bruno.getName() << endl;

	cout << bruno;
}

I am getting the following errors:

c:\visual studio projects\studentoverloader\student.h(18) : error C2804: binary 'operator <<' has too many parameters
c:\visual studio projects\studentoverloader\student.cpp(41) : error C2556: 'int __thiscall Student:perator <<(class std::basic_ostream<char,struct std::char_traits<char> > &,class Student)' : overloaded function differs only by return type from 'c
lass Student __thiscall Student:perator <<(class std::basic_ostream<char,struct std::char_traits<char> > &,class Student)'
c:\visual studio projects\studentoverloader\student.h(18) : see declaration of '<<'
c:\visual studio projects\studentoverloader\student.cpp(41) : error C2371: '<<' : redefinition; different basic types
c:\visual studio projects\studentoverloader\student.h(18) : see declaration of '<<'
main.cpp

I really really would appreciate any help at all, it is not urgent, or for anything in particular, i am just stuck.

Best regards, global

Thank you for your quick reply, it is very much appreciated.

Your code / better implementation of overloading reduced a lot of errors (nearly all of them in fact). I just have a small problem.

If i use:

Code:

class Student
{
	private:
		int loan;
		string name;

	public:
		friend std::ostream& operator<<(std::ostream& out, const Student& student);
};

With

Code:

Student ostream& operator<<(std::ostream& out, const Student& student)
{
	Student studentn;
	out << studentn.getName();
	out << studentn.getLoan();

	return student;
}

In my source/implementation file i get quite a few errors (about 5 nasty ones, it looks quite wrong).

But if i change it too:

Code:

ostream& operator<<(std::ostream& out, const Student& student)
{
	Student studentn;
	out << studentn.getName();
	out << studentn.getLoan();

	return out;
}

I dont get any compile errors at all. However, it does not work because all i get is '0' in the output.

However, thanks to your help, i feel i am almost there. Apologies if i am being stupid.

Best regards, global

Thank you.

I did try that and i got the same error repeated 3 times:

'getName' : cannot convert 'this' pointer from 'const class Student' to 'class Student &'

'getLoan' : cannot convert 'this' pointer from 'const class Student' to 'class Student &'

error C2440: 'return' : cannot convert from 'const class Student' to 'class std::basic_ostream<char,struct std::char_traits<char> > &'

Thank you, once again for your help and advice. It is very much appreciated.

Best regards, global

yay - i got it to work (when i say 'i', what i mean is 'you' ) - thanks, i changed it to:

return out;

and got rid of the constants.

I am a very happy person.

Thank you for your quick responses and help.

Best regards, global

I'm beginning to understand these overloaded operators now I think.

Code:

Student::operator<< (ostream &out, Student)
{
	Student studentn;
	out << studentn.getName();
	out << studentn.getLoan();

	return studentn;
}

or I guess now it's

Code:

Student::operator<< (ostream &out, Student)
{
	Student studentn;
	out << studentn.getName();
	out << studentn.getLoan();

	return out;
}

is better than just having a function like

Code:

Student::Output(Student)
{
Student studentn;
cout << studentn.getName();
.
.
.
}

. How so is this?

It's better than having a normal function because it is overloaded. You have all the functionality of the normal cout << operator, only with as much other functionality as you want. If you tried to replicate all of that inside a function it could get pretty messy. The compiler knows which << operator you are trying to use automatically.

Regards, global