class A
{
public:
    B component;
    int counter;
}

//First option
class A;
class B
{
public:
    update(A& boss)
    {
        A.couter++;
    }
}

//Second option
class A;
class B
{
public:
    A* refToBoss;
    update()
    {
        refToBoss->counter++;
    }
}