Call private member within the method belonging to the class itself - c++

Question

I encountered this problem when implementing a class:
class Cell {
bool isAlive;
int numNeighbours;
//...omit irrelavent private members
public:
Cell(); // Default constructor
~Cell(); // Destructor
void setLiving();
....
};
void Cell::setLiving(){
isAlive=true;
}
class Grid{...
friend std::ostream& ::operator(std::ostream& out, const Grid &g);
};//...omit
std::ostream& ::operator<<(std::ostream &out, const Grid &g){
int i,j;
for(i=0;i<g.gridSize;i++){
for(j=0;j<g.gridSize;j++){
if(**g.theGrid[i][j].isAliv*e*) out<<"X";
else out<<"_";
}
out<<endl;
}
return out;
}
The complier said that "isAlive" is a private member so I can't call it that way
I think the problem is at "g.theGrid[i][j].isAlive"
I tried to friend class Grid but it didnt help

Answer 1

You mentioned operator<< — it's most likely a free function, so it needs to be declared as friend to be able to access private members.
class Cell {
friend std::ostream& operator<<(std::ostream&, const Grid&);
// ...
};

Answer 2

The class member isAlive is private, so the operator didn't have the right to access it, you need to put a friend declaration in the body of Cell's definition.
class Cell {
friend std::ostream& operator<<(std::ostream&, const Cell&);
// ...
};

Answer 3

This line
if(**g.theGrid[i][j].isAlive) out<<"X"
Is accessing the private member 'isAlive'. I assume theGrid is a two dimensional array of Cell objects. You need a getLiving() method defined. Then use it here.

Answer 4

isAlive is private, declare it as public...
EDIT1:
class Cell {
public:
bool isAlive;
Update:
private members of a class are accessible only from within other members of the same class or from their friends.
protected members are accessible from members of their same class and from their friends, but also from members of their derived classes.
Finally, public members are accessible from anywhere where the object is visible.