lightsoff.cpp

TextDisplay *textDisplay = new TextDisplay();
Grid *grid = new Grid(n, n);
// Create a cell for every single slot.
for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
        grid->setCell(i, j, new Cell());    
    }
}

// Set observers for every single cell.
for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
        Cell *currentCell = grid->getCell(i, j);
        
        Cell [] adjacentCells = grid->getAdjacentCells(i, j);
        // if i=2 and j=2, then getAdjacentCells would return
        // grid.getCell(1,2), grid.getCell(2, 1), grid.getCell(3, 2), and grid.getCell(2, 3)
        for (Grid *adjacentCell : adjacentCells) { // This syntax probably doesn't exist in C++03 or whatever you use but you get my point
            currentCell->addObserver(adjacentCell);
        }
        
        currentCell->addObserver(textDisplay);
        
        // And then, for example, you do this:
        currentCell->notifyAllObservers("I was clicked")
    }
}

public void Cell::notifyAllObservers(String event) {
    for (Observer *observer : this.observers) {
        observer->notify(event);
    }
}

public void Cell::notify(String event) {
    if (event == "I was clicked") {
        this.onStatus = !this.onStatus;
        this.notifyAllObservers("I switched status");
    }
}

public void TextDisplay::notify(String event) {
    if (event == "I switched status") {
        this.redraw();
    }
}