Define OnClick.AddListener using for loop variable

I have an inventory UI script where I want to populate an array of the buttons for each slot and set an AddListener for each button - but do this from a loop:

Code (csharp):

1. private Button[] InventoryUIButton;
2. ...
3. private void Start()
4.     {
5.     InventoryUIButton = new Button[GlobalParams.NumberOfInventorySlots];
6. ...
7.         // Get all the UI buttons for each slot and set listener
8.         for (int i = 0; i < GlobalParams.NumberOfInventorySlots; i++)
9.         {
10.             InventoryUIButton[i] = InventoryUISlotsParent.transform.GetChild(i).gameObject.transform.GetChild(0).gameObject.GetComponent<Button>();
11.             InventoryUIButton[i].onClick.AddListener(() => ProcessInventoryButton(i));
12.         }
13.  
14. ...
15.  
16.     private void ProcessInventoryButton(int buttonIndex)
17.     {
18.         Debug.Log("Button hit " + buttonIndex);
19.     }

My intention is that when I click on button 4, I would see "Button hit 4", but instead every button results in ouput "Button hit 8" (as I currently have it set to have 8 inventory slots.)

So I'd like to declare the AddListener using the variable at time of setting it, but not reference the variable later on - if that makes sense.

I've tried the AddListener with a delegate but same results.

Code (csharp):

1. InventoryUIButton[i].onClick.AddListener(delegate { ProcessInventoryButton(i); });

Have found a few threads on here that seem to address this, but I'm still unclear how to achieve this.

 

You need to make a copy of the loop variable when doing this

Code (CSharp):

1. private Button[] InventoryUIButton;
2. ...
3. private void Start()
4.     {
5.     InventoryUIButton = new Button[GlobalParams.NumberOfInventorySlots];
6. ...
7.         // Get all the UI buttons for each slot and set listener
8.         for (int i = 0; i < GlobalParams.NumberOfInventorySlots; i++)
9.         {
10.             InventoryUIButton[i] = InventoryUISlotsParent.transform.GetChild(i).gameObject.transform.GetChild(0).gameObject.GetComponent<Button>();
11.  
12.             int iCopy = i;
13.             InventoryUIButton[i].onClick.AddListener(() => ProcessInventoryButton(iCopy));
14.         }
15. ...
16.     private void ProcessInventoryButton(int buttonIndex)
17.     {
18.         Debug.Log("Button hit " + buttonIndex);
19.     }

 

Ah, right - got it. Thank you, works great!!!