Objects Accessing Variables of Container Class - C++ - c++

Question

How can an object access a variable belonging the class containing it?
Right now I have a class called system that contains some other objects, and those objects need to access and modify one of the variables in the System class.
Example:
Class System {
BlockA _blockA = new BlockA();
BlockB _blockB = new BlockB();
BlockC _blockC = new BlockC();
BlockD _blockD = new BlockD();
int myVariable;
...stuff...
}
Class BlockA {
...stuff...
void someFunction () {
System.myVariable++;
}
...stuff...
}
etc...

Answer 1

Alright so I thought about this some more and realized that when initializing the objects, I will pass a pointer to the variable of interest. That way all objects can read that variable. For anyone else with this problem, if you need to write, you'll have to make sure that the variable is atomic.

Answer 2

Hard to know exactly what you're after, but appears something along these lines:
#BlockA.h
#ifndef BLOCKA_H
#define BLOCKA_H
class System;
class BlockA {
System* sys;
public:
BlockA(System* sys) : sys(sys) {}
void SomeFunction();
};
#endif // BLOCKA_H
#BlockA.cpp
#include "System.h"
void BlockA::SomeFunction() {
sys->setMyVariable(sys->getMyVariable() + 1);
}
#System.h
#ifndef SYSTEM_H
#define SYSTEM_H
class BlockA;
class System {
BlockA* _blockA;
int myVariable;
public:
System();
int getMyVariable() const;
void setMyVariable(int value);
BlockA& getBlockA() const;
};
#endif // SYSTEM_H
#System.cpp
#include "System.h"
#include "BlockA.h"
System::System()
: _blockA(new BlockA(this)) { }
int System::getMyVariable() const {
return myVariable;
}
void System::setMyVariable(int value) {
myVariable = value;
}
BlockA& System::getBlockA() const {
return *_blockA;
}