Resolved Question with Populating Button Listener with For Loop

I am populating my buttons array with the following code, all of the button clicks are printing the length of the array instead of individual index.

Code (CSharp):

1.         for (int i = 0; i < buttons.Length; i++)
2.             buttons[i].onClick.AddListener(() => Debug.Log(i));

Why does this happen?

 

Your loop is incrementing the value of i each time. Once the loop is complete then the value of i will be the same as the value of buttons.length. When you click the button, Debug.Log will show the value of i as it is now, not the value when the listener was assigned.

 

Delegate / Action variable capture / value capture:

https://forum.unity.com/threads/dyn...s-with-parameter-passing.974346/#post-6334800

A very nice summary by Bunny83;

https://forum.unity.com/threads/changing-name-of-method-call-at-runtime.1330029/#post-8404941

 

And this can be avoided by assigning

i

to a new variable which is declared inside the body of the for statement, and using this variable in the lambda expression instead.

Code (CSharp):

1. for(int i = 0; i < buttons.Length; i++)
2. {
3.    int index = i;
4.    buttons[index].onClick.AddListener(() => Debug.Log(index));
5. }