Why does the: ''call to non-static member function without an object argument'' error occur?

Question

How to solve the problem - call to non-static member function without an object argument? I have the sample detail:

The output looking like:
 f1 = 3/6, f2 = 4/5 
 f1 + f2 = 39/30 = 13/10 = 1.3 
 f1 - f2 = -9/30 = -3/10 = -0.3 
 f1 * f2 = 12/30 = 2/5 = 0.4 
 f1 / f2 = 15/24 = 5/8 = 0.625 
 Enter a fraction [numerator denominator]: 2 5 
 You entered 2/5

#include "Fraction.h"
 
 #include <iostream>
 
 using namespace std;
 
 Fraction::Fraction(const int numerator, const int denominator) { }
 
 int Fraction::getNumerator() const {
  return numerator;
 }
 
 int Fraction::getDenominator() const {
  return denominator;
 }
 
 int Fraction::gcd() const {
  int n = numerator;
  int d = denominator;
  int temp;
 
  while (d!=0) {
  temp = n % d;
  n = d;
  d = temp;
  }
 
  return n;
 
 }
 
 void Fraction::setNumerator(const int numerator) {
  this->numerator = numerator;
 }
 
 void Fraction::setDenominator(const int denominator) {
  this->denominator = denominator;
 }
 
 string Fraction::toString() const {
  return "";
 }
 
 double Fraction::returnDecimal() const {
  double a = (double) getNumerator();
  double b = (double) getDenominator();
 
  return (a / b);
 }
 
 void Fraction::reduce() {
 
  int a = gcd();
  int b = numerator / a;
  int c = denominator / a;
 
  setNumerator(b);
  setDenominator(c);
 
 }
 
 Fraction Fraction::operator +(const Fraction& f) const {
 
  Fraction temp;
 
  int a = getNumerator();
  int b = getDenominator();
  int c = f.getNumerator();
  int d = f.getDenominator();
 
  int tempOne = b;
  int tempTwo = d;
 
  a = a * tempTwo;
  b = b * tempTwo;
 
  c = c * tempOne;
  d = d * tempOne;
 
  temp.setNumerator(a+c);
  temp.setDenominator(d);
 
  return temp;
 
 }
 
 Fraction Fraction::operator -(const Fraction& f) const {
 
  Fraction temp;
 
  int a = getNumerator();
  int b = getDenominator();
  int c = f.getNumerator();
  int d = f.getDenominator();
 
  int tempOne = b;
  int tempTwo = d;
 
  a = a * tempTwo;
  b = b * tempTwo;
 
  c = c * tempOne;
  d = d * tempOne;
 
  temp.setNumerator(a-c);
  temp.setDenominator(d);
 
  return temp;
 
 }
 
 Fraction Fraction::operator *(const Fraction& f) const {
 
  Fraction temp;
 
  temp.setNumerator(getNumerator() * f.getNumerator());
  temp.setDenominator(getDenominator() * f.getDenominator());
 
  return temp;
 
 }
 
 Fraction Fraction::operator /(const Fraction& f) const {
 
  Fraction temp;
 
  temp.setNumerator(getNumerator() * f.getDenominator());
  temp.setDenominator(getDenominator() * f.getNumerator());
 
  return temp;
 
 }
 
 bool Fraction::operator ==(const Fraction& f) const {
 
  return ( (getNumerator() == f.getNumerator()) && (getDenominator() == f.getDenominator()) );
 
 }
 
 bool Fraction::operator !=(const Fraction& f) const {
 
  return !( (getNumerator() == f.getNumerator()) && (getDenominator() == f.getDenominator()) );
 
 }
 
 bool Fraction::operator <(const Fraction& f) const {
 
  double a = getNumerator();
  double b = getDenominator();
 
  double c = getNumerator();
  double d = getDenominator();
 
  return ((a/b) < (c/d));
 
 }
 
 bool Fraction::operator <=(const Fraction& f) const {
 
  double a = getNumerator();
  double b = getDenominator();
 
  double c = getNumerator();
  double d = getDenominator();
 
  return ((a/b) <= (c/d));
 
 }
 
 bool Fraction::operator >(const Fraction& f) const {
 
  double a = getNumerator();
  double b = getDenominator();
 
  double c = getNumerator();
  double d = getDenominator();
 
  return ((a/b) > (c/d));
 
 }
 
 bool Fraction::operator >=(const Fraction& f) const {
 
  double a = getNumerator();
  double b = getDenominator();
 
  double c = getNumerator();
  double d = getDenominator();
 
  return ((a/b) >= (c/d));
 
 }
 
 ostream& operator <<(ostream& out, const Fraction& f) {
  out << f.getNumerator() << "/" << f.getDenominator();
 
  return out;
 }
 
 istream& operator >>(istream& in, Fraction& f) { 
 
  int a;
  int b;
 
  in >> a >> b;
 
  f.setNumerator(a);
  f.setDenominator(b);
 
  return in;
 
 }

#include <iostream>
 #include "Fraction.h"
 #include "Fraction.cpp"
 using namespace std;
 
 int main(int argc, const char * argv[])
 {
 
  Fraction::getNumerator() const;
  Fraction::getDenominator() const;
  Fraction::gcd() const;
  Fraction::setNumerator(<#const int numerator#>);
  Fraction::setDenominator(<#const int denominator#>);
  Fraction::toString();
  Fraction::returnDecimal() const;
  Fraction::reduce();
 
  return 0;
 }

#include <iostream>
 #include <string>
 
 using namespace std;
 
 class Fraction {
 
 private:
 
  int numerator;
 
  int denominator;
 
  int gcd() const;
 
 public:
 
  Fraction(const int numerator = 0, const int denominator = 0);
 
  int getNumerator() const;
 
  int getDenominator() const;
 
  void setNumerator(const int numerator);
 
  void setDenominator(const int denominator);
 
  string toString() const;
 
  double returnDecimal() const;
 
  void reduce();
 
  bool operator ==(const Fraction& f) const;
 
  bool operator !=(const Fraction& f) const;
 
  bool operator <(const Fraction& f) const;
 
  bool operator <=(const Fraction& f) const;
 
  bool operator >(const Fraction& f) const;
 
  bool operator >=(const Fraction& f) const;
 
  Fraction operator +(const Fraction& f) const;
 
  Fraction operator -(const Fraction& f) const;
 
  Fraction operator *(const Fraction& f) const;
 
  Fraction operator /(const Fraction& f) const;
 
  friend ostream& operator <<(ostream&, const Fraction&);
 
  friend istream& operator >>(istream&, Fraction&);
 
 };

While I was running it, I found the warning message:

call to non-static member function without an object argument

That is my question in my midterm exam, and it is urgent. I searched the solutions on some websites, but I didn't get it. I may miss any line or other changes. I appreciate your assistance!

lyytutoria · Accepted Answer

The cause: You got this error because you are trying to access the functions of a class but you don't instantiate it. Solution: Fraction is a class, so before using its (not static) functions, you need create an object of that class. You can do as following:

Fraction f; f.getNumerator();

Gabriel Pons · Answer

Fraction is a type of class. To call the nonstatic functions of this class, you need an object from that class.

Fraction f;
f.getNumerator();

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