'fArray' was not declared in this scope - c++

Question

Hello I'm having this issue with my C++ problem I'm working on.
Here is the code
Cell.h
#ifndef CELL_H
#define CELL_H
#include <iostream>
#include <stdlib.h>
#include <time.h>
using namespace std;
class Cell
{
private:
int level;
int row;
int column;
//declares a variable called ptrFunction_array which is an array of 3 function pointers.
typedef void (*ptrFunction[])(void);
static void function1()
{
cout << "I'm function 1";
}
static void function2()
{
cout << "I'm function 2";
}
static void function3()
{
cout << "I'm function 3";
}
public:
Cell(int currentLevel, int currentRow, int currentColumn)
{
level = currentLevel;
row = currentRow;
column = currentColumn;
ptrFunction = new *fArray[3];
fArray[0] = function1();
fArray[1] = function2();
fArray[2] = function3();
}
virtual ~Cell();
void tick()
{
int randomNumber = rand() % 3;
cout << "Cell(" << level << ", " << row << ", " << column << ") ";
fArray[randomNumber];
}
};
#endif // CELL_H
Main.cpp
#include <iostream>
#include <stdlib.h>
#include <time.h>
#include "Cell.h"
using namespace std;
Cell ****myArray;
int main()
{
int level = 0;
int row = 0;
int column = 0;
char userInput = 'y';
srand (time(NULL));
do
{
cout << "Please input the amount of levels: ";
cin >> level;
cout << "Please input the amount of rows: ";
cin >> row;
cout << "Please input the amount of columns: ";
cin >> column;
cout << endl;
myArray = new Cell *** [level];
// Set random number to the elements of the array
for (int currentLevel = 0; currentLevel < level; currentLevel++)
{
myArray [currentLevel] = new Cell ** [row];
for (int currentRow = 0; currentRow < row; currentRow++)
{
myArray [currentLevel][currentRow] = new Cell * [column];
for (int currentColumn = 0; currentColumn < column; currentColumn++)
{
myArray [currentLevel][currentRow][currentColumn] = new Cell (currentLevel, currentRow, currentColumn);
myArray [currentLevel][currentRow][currentColumn] -> tick();
cout << " ";
}
cout << endl;
}
cout << endl;
}
cout << "Do you want to try again? (y / n) ";
cin >> userInput;
cout << endl;
if ((userInput == 'y') || (userInput == 'Y'))
{
for (int currentLevel = 0; currentLevel < level; currentLevel++)
{
for (int currentRow = 0; currentRow < row; currentRow++)
{
for (int currentColumn = 0; currentColumn < column; currentColumn++)
{
delete[] myArray[currentLevel][currentRow][currentColumn];
}
delete[] myArray[currentLevel][currentRow];
}
delete[] myArray[currentLevel];
}
delete[] myArray;
myArray = NULL;
}
}while (userInput != 'n');
return 0;
}
I notice that my fArray isn't inside the scope. the Line ptrFunction = new *fArray[3]; is where my error is. I've recently started learning C++ so I'm in the process of trying to understand why my typedef void (*ptrFunction[])(void); isn't correctly initializing the fArrayfor my program. The goal of my program is to be able to create a 3 dimensional array and be able to point to the Cell Objects and be able to track the location x,y,z.
Why does an error like this happen?

Answer 1

I'm going to ignore the four star pointer for now and stick to what's giving OP the most immediate grief.
A quick walk-through:
Cell(int currentLevel, int currentRow, int currentColumn)
{
level = currentLevel;
row = currentRow;
column = currentColumn;
Not bad to here. But...
ptrFunction = new *fArray[3];
This says assign to the variable ptrFunction, which must already exist and doesn't, a newly allocated array of 3 fArrays. The problem here is ptrFunction has been defined as a type, not a variable. fArray is not a type.
fArray[0] = function1();
fArray[1] = function2();
fArray[2] = function3();
Use fArray as a variable, making what's gone wrong here somewhat clear.
}
Cell needs to look a bit more like this, but not exactly. More on that later.
Cell(int currentLevel, int currentRow, int currentColumn)
{
level = currentLevel;
row = currentRow;
column = currentColumn;
ptrFunction * fArray = new ptrFunction[3];
Now fArray is a variable that points to one or more objects of type ptrFunction (but the definition of ptrFunction is somewhat broken), and points fArray at three ptrFunctions. Technically it points at the first of three ptrFunctions.
fArray[0] = function1();
fArray[1] = function2();
fArray[2] = function3();
}
Now we have an fArray, but it is a local variable and it only exists between the curly braces of Cell's constructor. When the constructor exists, the pointer goes away. The memory allocated does not and is lost. Without fArray pointing to it, you can't easily find it to use or delete it. fArray needs wider scope so that A) the memory isn't lost, and B) so that tick and other members of Cell can see it.
class Cell
{
private:
ptrFunction * fArray;
int level;
and in the constructor:
Cell(int currentLevel, int currentRow, int currentColumn)
{
level = currentLevel;
row = currentRow;
column = currentColumn;
fArray = new ptrFunction[3];
That fixes the can't find fArray.
My recommendation is to get one Cell working and then take a stab at getting a 1 dimensional array of Cells working. When you have one dimension, then try two. You might find that's all you need.
Edit
Forgot to mention this: Function pointers to members functions are an absolute expletive deleted to get right. Here is a page on common pitfalls and how to avoid them.
And here is how we avoid this smurf in the here and now of Modern C++: std::bind and std::function. The tutorials at the bottom of the linked document pages probably describe how to use them for simple cases better than I can.