Array in for loop gives array index out of range exception

Question

Here is my code:

ShopButton[] allButtons = FindObjectsOfType<ShopButton> ();

for (int i = 0; i < allButtons.Length; i++) 
{
    allButtons [i].UpdateButtonState ((GameDataManager.publicInstance.skinAvailability & 1 << allButtons [i - 1].ninjaNumber) == 1 << allButtons [i - 1].ninjaNumber);
}

When I run it this code gives me an IndexOutOfRangeException .

Answer 1

I think the reason is because of the first index that causes a problem. if i starts with 1 then i-1 will be 0 and therefore the index 0 exists in array allbuttons. Clearly : if starting i is 0 , then i-1 will be -1 ; this will cause index out of range exception because all arrays start with index 0 and have no index -1. ;

Starting with i = 1 the error will be solved because then i-1 will be 0 which is in range of indexes of any array.

change part of loop to :

for (int i = 1; i < allButtons.Length; i++)