Unity - one Dropdown callback for multiple Dropdown components

Question

I have a UI with a number of dropdown controls, each affecting one of an array or items. I use onValueChanged(int index), each hooked up to its own listener (selected01(), selected02() ... etc).

This is a bit messy. It would be much better to have one callback - selected(Dropdown instance, int index) - which handles all of them. The callback would identify the control from the instance parameter and act on the appropriate array item.

I cannot see how to do that - onValueChanged() only provides an index not the source. Yet I am sure I have seen a solution to this, possibly involving a Delegate, but cannot now find it.

Any suggestions? (The same could apply to any array of controls, not just Dropdowns).

Answer 1

As far as I could see onValueChanged anyway returns the instance of DropDown that was changed.

---

Maybe that is different in the version you are using.

You can simply create your own listener method and do e.g.

public DropDown[] dropdowns;

private void HandleChange(DropDown dropdown, int newIndex)
{
    // Your stuff here
}

...

foreach(var dropdown in dropdowns)
{
    var currentDropdown = dropdown;
    currentDropdown.onValueChanged.AddListener((newIndex) => { HandleChange(currentDropdown, newIndex); });
}