SFML/C++ cells won't move - c++

Question

I am currently trying to make a cellular automata. I am just getting the basics of direction, movement and rendering.
However, when running the compiler the cells don't move despite calling the Move function.
Here are the files,
Cell.cpp
#include "Cell.h"
#include "CellManager.h"
Cell::Cell()
{
Lifetime = 5 + rand() % 2 - 1;
}
Cell::~Cell()
{
}
void Cell::Move(int dir)
{
switch (dir)
{
default: y -= 2;
break;
case 0: y -= 2;
break;
case 1: x += 2;
break;
case 2: y += 2;
break;
case 3: x -= 2;
break;
}
if (x > 800)
{
x = 0;
} else if (x < 0)
{
x = 800;
}
if (y > 800)
{
y = 0;
}
else if (y < 0)
{
y = 800;
}
}
int Cell::ChangeDir(int dir)
{
dir = rand() % 3;
return dir;
}
void Cell::Draw(sf::RenderTarget& target)
{
sf::RectangleShape cell;
cell.setSize(sf::Vector2f(2.f,2.f));
cell.setOutlineColor(colour);
cell.setPosition(x, y);
target.draw(cell);
}
void Cell::SetUp(int X, int Y, sf::Color Colour, int dir)
{
x = X;
y = Y;
colour = Colour;
Dir = dir;
}
CellManager.cpp
#include "CellManager.h"
#include "Cell.h"
void CellManager::UpdateCells(vector<Cell> cells, sf::RenderTarget& target)
{
for (int i = 0; i < cells.size(); i++)
{
cells[i].ChangeDir(cells[i].Dir);
cells[i].Move(cells[i].Dir);
cells[i].Draw(target);
}
}
void CellManager::CreateInstance()//TODO
{
}
I do not understand where I am going wrong as the switch statement works but the cells just refuse to move. Any help would be appreciated :)

Answer 1

Your function, CellManager::UpdateCell's parameter vector<Cell> cells COPIES the vector of cells, then changes the copies. You probably want to pass by reference instead. This would look like: std::vector<Cell>& cells.
Other note:
ChangeDir does not change the member variable Dir. You could pass in by reference for that as well, or just not pass in anything at all and use Dir = rand() % 3;.