How to associate a number to a button and get that number when the user clicks on the button?

Question

I am creating buttons for each level through script as shown below

private void CreateLevelButtons()
{
    for (int i = 1; i <= no_of_levels; i++)
    {
        Button button = Instantiate(button_prefab);
        button.GetComponentInChildren<Text>().fontSize = 12;
        button.GetComponentInChildren<Text>().text = "Level " + i.ToString();
        button.transform.SetParent(content.transform, false);
        button.onClick.AddListener(() => OnClickLevelButton());
    }
}

In OnClickLevelButton() function I want to determine the level number of the button that was clicked. Is there a way to associate a number to a button so that i can access that number later when the user clicks on the button?

Answer 1

Yes it is possible, but you have to take care of the closure problem. In order to avoid this, create a temporary variable like this:

private void CreateLevelButtons()
{
    for (int i = 1; i <= no_of_levels; i++)
    {
        int index = i ; // Create variable to avoid closure problem
        Button button = Instantiate(button_prefab);
        button.GetComponentInChildren<Text>().fontSize = 12;
        button.GetComponentInChildren<Text>().text = "Level " + i.ToString();
        button.transform.SetParent(content.transform, false);
        button.onClick.AddListener(() => OnClickLevelButton( index ));
    }
}

void OnClickLevelButton( int i )
{
    Debug.Log("Button #" + i + " has been clicked!");
}