Giving one class Access to another C++ - c++

Question

I am trying to access a member of one class in another class. I am fairly new to C++ so forgive me if this is an easy fix but I cannot find the answer, so I came here.
In this instance I would like to call "init();" from class CGuessNumber and member CheckNumber.
Here is my code.
#include <iostream>
#include <ctime>
#include <cstdlib>
class CGuessNumber
{
public:
int GenerateNumber()
{
return rand() % 100 + 1;
}
void checkNumber(int guess, int answer, int &attempts)
{
if (guess < answer)
{
std::cout << "TOO LOW, TRY AGAIN" << "\n" << "TRYS LEFT: " << attempts << "\n";
attempts--;
}else if(guess > answer)
{
std::cout << "TOO HIGH, TRY AGAIN" << "\n" << "TRYS LEFT: " << attempts << "\n";
attempts--;
}else if(guess == answer)
{
std::cout << "YOU WON!" << "\n" << "TRYS LEFT: " << attempts << "\n";
}
if (attempts <= 0)
{
std::cout << "YOU LOST!" << "\n" << "TRYS LEFT: " << attempts << "\n";
CGAME::init(answer, attempts);
}
}
}Number;
class CGAME
{
public:
void init(int &answer, int &attempts)
{
answer = Number.GenerateNumber();
attempts = 5;
};
int newGame()
{
srand (time(NULL));
int intAnswer, playerGuess, trys;
init(intAnswer, trys);
while(intAnswer != playerGuess and trys > 0)
{
std::cin >> playerGuess;
Number.checkNumber(playerGuess, intAnswer, trys);
}
};
}ONewGame;
int main()
{
CGAME ONewGame
ONewGame.newGame();
return 0;
}

Answer 1

I think, this is what you're looking for
Basically you can pass a pointer which points to one object into a constructor of the other. In this case we just pass a pointer to CGuessNumber into the CGAME constructor, we also store this pointer in a private field so we can use it. Then you can use this pointer to call methods.
working example (pointer->method syntax)
working example (reference.method syntax)
#include <iostream>
#include <ctime>
#include <cstdlib>
class CGuessNumber
{
public:
int GenerateNumber()
{
return rand() % 100 + 1;
}
void checkNumber(int guess, int answer, int &attempts)
{
if (guess < answer)
{
std::cout << "TOO LOW, TRY AGAIN" << "\n" << "TRYS LEFT: " << attempts << "\n";
attempts--;
}else if(guess > answer)
{
std::cout << "TOO HIGH, TRY AGAIN" << "\n" << "TRYS LEFT: " << attempts << "\n";
attempts--;
}else if(guess == answer)
{
std::cout << "YOU WON!" << "\n" << "TRYS LEFT: " << attempts << "\n";
}
if (attempts <= 0)
{
std::cout << "YOU LOST!" << "\n" << "TRYS LEFT: " << attempts << "\n";
}
}
};
class CGAME
{
public:
CGAME(CGuessNumber* pNumber)
{
m_number = pNumber;
}
void init(int &answer, int &attempts)
{
answer = m_number->GenerateNumber();
attempts = 5;
};
void newGame()
{
srand (time(NULL));
int intAnswer, playerGuess, trys;
init(intAnswer, trys);
while(intAnswer != playerGuess and trys > 0)
{
std::cin >> playerGuess;
m_number->checkNumber(playerGuess, intAnswer, trys);
}
};
private:
CGuessNumber* m_number;
};
int main()
{
CGuessNumber* pGnum = new CGuessNumber();
CGAME* ONewGame = new CGAME(pGnum);
ONewGame->newGame();
return 0;
}

Answer 2

Let me just address the syntax errors.
In the checkNumber() function:
...
CGAME::init(answer, attempts);
...
There are 2 problems with this:
CGAME is not declared yet, so the compiler doesn't know it exists, or what it is. To avoid this, usually all the classes are declared at the top (or in a header file) and all there functions are defined later.
You can't call a member function of a class without an object, unless it's a static function. This function can be static as it doesn't use member variables (there are design issues, but lets ignore them for now).
Also in main() you missed a ';', but I think you already know that :-)
So, applying these changes:
#include <iostream>
#include <ctime>
#include <cstdlib>
// only declaring the classes here
class CGAME
{
public:
static void init(int &answer, int &attempts);
int newGame();
}ONewGame;
class CGuessNumber
{
public:
int GenerateNumber();
void checkNumber(int guess, int answer, int &attempts);
}Number;
// defining all the class member functions now
int CGAME::newGame()
{
srand (time(NULL));
int intAnswer, playerGuess, trys;
init(intAnswer, trys);
while(intAnswer != playerGuess and trys > 0)
{
std::cin >> playerGuess;
Number.checkNumber(playerGuess, intAnswer, trys);
}
}
int CGuessNumber::GenerateNumber()
{
return rand() % 100 + 1;
}
void CGuessNumber::checkNumber(int guess, int answer, int &attempts)
{
if (guess < answer)
{
std::cout << "TOO LOW, TRY AGAIN" << "\n" << "TRYS LEFT: " << attempts << "\n";
attempts--;
}else if(guess > answer)
{
std::cout << "TOO HIGH, TRY AGAIN" << "\n" << "TRYS LEFT: " << attempts << "\n";
attempts--;
}else if(guess == answer)
{
std::cout << "YOU WON!" << "\n" << "TRYS LEFT: " << attempts << "\n";
}
if (attempts <= 0)
{
std::cout << "YOU LOST!" << "\n" << "TRYS LEFT: " << attempts << "\n";
CGAME::init(answer, attempts);
}
}
void CGAME::init(int &answer, int &attempts)
{
answer = Number.GenerateNumber();
attempts = 5;
}
int main()
{
CGAME ONewGame;
ONewGame.newGame();
return 0;
}