reverse function doesn't reverse the referenced string of a class instantiation - c++

Question

I'm trying to reverse the string from the FunnyNumber class. The problem is that when I call the method reverse in main on f2, it doesn't reverse the f2 string. But when I print out the reversed string from the reverse method implementation, it works. Also I overloaded the << operator to print out the string value in the class Number which is inherited in FunnyNumber class. Any help would be appreciated.
#ifndef NUMBER_H
#define NUMBER_H
#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
class Number {
public:
// Make a number with value 0
Number();
// Make a number with value val
Number(string val);
// Get the number's value
virtual string getValue() const;
// Print this number to the stream
virtual void print(ostream& stream) const;
// Read this number from the stream
virtual void read(istream& stream);
// Overload the insertion operator
friend ostream& operator <<(ostream& outs, const Number& n);
// Overload the extraction operator
friend istream& operator >> (istream& ins, Number& n);
protected:
string value;
};
#endif
Number::Number()
{
value = "";
}
Number::Number(string args)
{
value = args;
}
string Number::getValue()const
{
return value;
}
ostream& operator <<(ostream& outs, const Number& n)
{
n.print(outs);
return outs;
}
void Number::print(ostream& stream)const
{
stream << getValue();
}
void Number::read(istream& stream)
{
stream >> value;
}
istream& operator >> (istream& ins, Number& n)
{
n.read(ins);
return ins;
}
#ifndef FUNNYNUMBER_H
#define FUNNYNUMBER_H
#include<iostream>
#include<string>
#include"Number.h"
#include<algorithm>
using namespace std;
class FunnyNumber : public Number
{
public:
FunnyNumber();
FunnyNumber(string val);
virtual string operator+(const FunnyNumber &other)const;
virtual bool operator==(const FunnyNumber &other)const;
void reverse();
int find_first_not_this(char a);
protected:
string value;
};
#endif // !FUNNYNUMBERS_H
FunnyNumber::FunnyNumber()
{
value = "";
}
FunnyNumber::FunnyNumber(string val) : Number(val)
{
value = val;
}
string FunnyNumber::operator+ (const FunnyNumber& other)const
{
return getValue() + other.getValue();
}
int FunnyNumber::find_first_not_this(char a)
{
int pos = 0;
for(int i = 0; i < value.length(); i++)
{
if(value[i] != a)
{
pos = i;
return pos;
}
}
return pos;
}
bool FunnyNumber::operator==(const FunnyNumber& other)const
{
bool isEqual = true;
for (int i = 0; i < other.getValue().length(); i++)
{
bool found = false;
for (int j = 0; j < getValue().length(); j++)
{
if(getValue()[j] == other.getValue()[i])
{
found = true;
break;
}
}
if(!found)
{
isEqual = found;
return isEqual;
}
}
return isEqual;
}
void FunnyNumber::reverse()
{
std::reverse(value.begin(), value.end());
value.erase(0, find_first_not_this('0'));
}
#include <iostream>
#include<string.h>
#include "FunnyNumber.h"
using namespace std;
int main()
{
FunnyNumber f2;
f2 = FunnyNumber("223");
f2.reverse();
cout<<"Reversed value "<<f2<<endl;
system("pause");
return 0;
}
output is 223 instead of 322

Answer 1

Your FunnyNumber stores the value twice, once in a subobject of type Number, and once in string FunnyNumber::value.
Your reverse function modifies the second one, but doesn't have any effect on the Number base subobject. And then the only output function you call is working on the Number base subobject, and knows nothing about string FunnyNumber::value. That's why what is printed is not the result of reversal.

Answer 2

the overloaded operator << is a friend function on the Number class and friend functions are not inherited.
class Number {
public:
// Make a number with value 0
Number();
// Make a number with value val
Number(string &val);
// Get the number's value
virtual string getValue() const;
// Print this number to the stream
virtual void print(ostream& stream) const;
// Read this number from the stream
virtual void read(istream& stream);
// Overload the insertion operator
friend ostream& operator <<(ostream& outs, const Number& n);
// Overload the extraction operator
friend istream& operator >> (istream& ins, Number& n);
protected:
string *value;
};
Number::Number()
{
value = NULL;
}
Number::Number(string &args)
{
value = &args;
}
string Number::getValue()const
{
return *value;
}
ostream& operator <<(ostream& outs, const Number& n)
{
n.print(outs);
return outs;
}
void Number::print(ostream& stream)const
{
stream << getValue();
}
void Number::read(istream& stream)
{
stream >> *value;
}
istream& operator >> (istream& ins, Number& n)
{
n.read(ins);
return ins;
}