closure_rc_hashmap.rs

// Instantiate Option which will help us mutate the image
// from within the closure.
let image_wrapper: Rc<RefCell<Option<gtk::Image>>> = Rc::new(RefCell::new(None));

// (...)

// Bind action to the generate button
generate_button.connect_clicked(clone!(
        box_vert, image_wrapper, spiral, adj_x, radio_primes => move |_| {

    let window = match window_weak.upgrade() {
        Some(window) => window,
        None => return
    };

    // Remove existing image from the Option container
    let mut internal_image = image_wrapper.borrow_mut();
    let image = internal_image.as_ref().unwrap();
    box_vert.remove(image);

    // Create new image
    let image_gtk: gtk::Image = spiral.borrow().generate_to_gtk();

    let img_clone = image_gtk.clone();

    // Replace the reference to the newly generated image in the wrapper
    *internal_image = Some(image_gtk);

    // Put the reference of the new image to the layout container
    box_vert.pack_start(&img_clone, false, false, 20);

    window.show_all();
}));