How do I make multiple Unity buttons with UnityActions that depend on a variable?

Question

I am trying to instantiate multiple buttons in Unity. Each button has a UnityAction attached to it - on click it should call a function PlayLevel which depends on an int.

for (int i = 1; i <= 5; i++)
{
    GameObject button = Instantiate(buttonPrefab, buttonParent.transform);

    UnityAction action = new UnityAction(() => PlayLevel(i));
    button.GetComponent<UnityEngine.UI.Button>().onClick.AddListener(action);
    
}

buttonPrefab is an already assigned prefab dictating how the button should look, and buttonParent.transform is the parent object, again already assigned.

When I click any of the buttons, they all call PlayLevel with the parameter 6. It seems the UnityAction is not per object and is being reassigned each time i is changed, all the actions change.

How may I get this to work correctly?

Answer 1

There are two problems. First, new UnityAction(() => Play Level(i)) This is the lambda method that our friend mentioned

Second, the ring works incorrectly

For the first problem, we create a separate function to send UnityAction

public UnityAction GetUnityAction(int _lvl) => new UnityAction(() => { PlayLevel(_lvl); });

Second, you have changed the step count variable of the loop you wrote, you can change it to this loop

levelNumber = 5;
for (int i = 1; i <= levelNumber; i++)

This loop navigates from level 1 to the level you want. It can be changed depending on the variable.

Final code:

int levelNumber = 5;

public void SetButtons()
{
    for (int i = 1; i <= levelNumber; i++)
    {
        GameObject button = Instantiate(buttonPrefab, buttonParent.transform);
        button.GetComponent<UnityEngine.UI.Button>().onClick.AddListener(GetAction(i));
    }
}

public UnityAction GetAction(int _lvl) => new UnityAction(() => { PlayLevel(_lvl); });