class function inaccessible c++(beginner problem) - c++

Question

Hello so i want to create a header file class which name testing and also its cpp but for some reason this is inaccessible i dont know why
testing.h
#ifndef TESTING_H
#define TESTING_H
#include <string>
using namespace std;
class testing
{
string Name;
void printname(string name);
};
#endif
testing.cpp
#include <iostream>
#include "testing.h"
using namespace std;
void testing::printname(string name) // inaccessible in my main i dont know what reason :(
{
Name = name;
cout<<Name<<endl;
}
main
#include <iostream>
#include "testing.h"
using namespace std;
using std::string;
int main()
{
testing tester;
tester.printname("JPR"); //error since testing::printname is inaccessible no idea
return 0;
}

Answer 1

If you don't specify the visibility of the members, they are private.
You can either use a struct (visibility is public):
struct testing
{
string Name;
void printname(string name);
};
or you can specify that printname is public:
class testing
{
public:
void printname(string name);
private:
string Name;
};
Try the following:
testing.h
#ifndef TESTING_H
#define TESTING_H
#include <string>
class testing
{
public:
// Better to pass the parameter as const reference to avoid performing a copy.
void printname(const std::string& name);
private:
std::string Name;
};
#endif
testing.cpp
#include <iostream>
#include "testing.h"
void testing::printname(const std::string& name)
{
Name = name;
std::cout << Name << std::endl;
}
main.cpp
#include "testing.h"
int main()
{
testing tester;
tester.printname("JPR");
return 0;
}

Answer 2

In C++:
A class defined with the keyword class has private access for its members and its base classes by default.
Add public: access modifier to your class defition, to mark method as public:
class testing
{
string Name;
public:
void printname(string name);
};

Answer 3

when you create a class, every member function and member variable is set in default as private, which means that they won't be accessible. To make your function public you need to change this in your code:
class testing
{
private: //is private in default, i add it for better readabilty
string Name;
public:
void printname(string name);
};
Worth to mention that you (almost) ALWAYS want to keep all member variables private!