Problem with argument list

I am trying to learn how to build a class and I am having trouble. My simple program reads in a fraction, and inverts it. I will do much more with it later if I can get past this problem. Currently I have two warnings, one about missing an argument list, and the other about using frac1 without it being initialized. I've banged my head on this for 2 days now, so I think it is time I ask for some help. Here is the code...

Code:

---

#include <iostream>
using namespace std;

char oper;

class SingleFraction
{
public:
        void getFrac(SingleFraction ff1)
        {
                char misc;
                cin >> num >> misc >> den >> oper;
        }
        void invert(SingleFraction ff1)
        {
                num = ff1.den;
                den = ff1.num;
        }
        void display()
        {
                cout << num << '/' << den;
        }
private:
        int num, den;
};

int main()
{
        SingleFraction frac1, fracAns;
        char choice = 99;

        while (choice != 'n' && choice != 'N')
        {
                cout << "Enter a fraction and operator: ";
                frac1.getFrac;  // warning here about missing argument list
                switch(oper)
                {
                case 'i': fracAns.invert(frac1); break;  // warning here about frac1 not being initialized
                //default: cout << "Illegal operator.";
                        continue;
                }
                fracAns.display();
                cout << "Answer = "; fracAns.display();
                cout << "\nAgain(y/n)?: "; cin >> choice;
        }
        return 0;
}

---

try some thing more like this:

fracClass.h

Code:

---

#ifndef _fracClass_h_
#define _fracClass_h_

class SingleFraction
{
public:
        void getFrac();
        void invert();
        void display();
        char retOper()
private:
        int num, den;
        char oper;
};

#endif

---

fracClass.cpp

Code:

---

#include "fracClass.h"

void singleFraction::getFrac()
{
        char misc;
        cin >> num >> misc >> den >>oper;
}
void SingleFrac::invert()
{
                int temp=num;
        num = den;
        den = temp;
}
void SingleFrac::display()
{
        cout << num << '/' << den;
}
char SingleFrac::retOper()
{ return oper; }

---

main.cpp

Code:

---

#include<iostream>
#include "fracClass.h"

int main()
{
        SingleFraction frac1, fracAns;
        char choice = 99;

        while (choice != 'n' && choice != 'N')
        {
                cout << "Enter a fraction and operator: ";
                frac1.getFrac;  // warning here about missing argument list
                switch(frac1.oper)
                {
                case 'i': fracAns.invert(frac1); break;  // warning here about frac1 not being initialized
                //default: cout << "Illegal operator.";
                        continue;
                }
                fracAns.display();
                cout << "Answer = "; fracAns.display();
                cout << "\nAgain(y/n)?: "; cin >> choice;
        }
        return 0;
}

---