SFML update function not moving sprite - c++

Question

The current update function should be moving the sprite to the left 10 pixels every time it's called, but the sprite (cup1Sprite) is static and not moving. I tried using sprite.rotate(); and the sprite rotated every frame (which was expected), so something is wrong with the way I've written the update function for updating the sprite position. Can anyone suggest what's going wrong?
Code:
DrawCups.h
class DrawCups
{
public:
DrawCups(sf::RenderWindow& window);
~DrawCups();
void update();
void drawCup1();
private:
sf::RenderWindow& _window;
//Cup1
sf::Texture _cup1; // the texture which will contain our pixel data
sf::Sprite _cup1Sprite; // the sprite which will actually draw it
};
Update function in DrawCups.cpp
void DrawCups::update()
{
sf::Vector2f pos = this->_cup1Sprite.getPosition();
pos.x+=10;
this->_cup1Sprite.setPosition(pos);
}
main.cpp
int main()
{
sf::RenderWindow window(sf::VideoMode(1366, 768), "Sorting Algorithm Visualisation: SFML");
window.setFramerateLimit(60);
DrawCups drawToWindow(window);
while (window.isOpen())
{
sf::Event event;
while (window.pollEvent(event))
{
if (event.type == sf::Event::Closed)
window.close();
}
drawToWindow.update();
window.clear(sf::Color::White);
drawToWindow.drawBench();
drawToWindow.drawCup1();
window.display();
}
return 0;
}