In the second class I want to only add numbers to string, and I am getting the error "main.cpp:38:19: error: ‘virtual void NumericInput::add(char)’ is private within this context 38 | input->add('1');' for every time I class add for Numeric object. What did I do wrong here, isn't everything already public? Thank you!!

#include <string>
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
using namespace std;

class TextInput
{
    public:
    string s="";
    
    virtual void add(char c)
    {
        s =c;
    }
    string getValue()
    {
        return s;
    }
};



class NumericInput : public TextInput
{
    //modified
    void add(char c) 
    {
        if(isdigit(c))
        {
            s =c;
        }
    }
};

int main()
{
    NumericInput* input = new  NumericInput();
    input->add('1');
    input->add('a');
    input->add('0');
    cout<<input->getValue();
}

CodePudding user response：

All declarations in a class are private by default if there's no public access specifier. You should also override your virtual function in NumericInput.

CodePudding user response：

Add public before in NumericInput

class NumericInput : public TextInput
{
public:
    //modified
    void add(char c) 
    {
        if(isdigit(c))
        {
            s =c;
        }
    }
};