Array index out of range when I am inserting an element into the array

Question

I have an array that contains UIViews (cells) that starts empty. I set it's values when a function is fired by looping through a different array:

cells = [cell0, cell1, cell2, cell3, cell4]

// Code in function ↓

var cellAnimationArray: [NPFCarouselCell] = []

for cell in self.cells {
    if cell.frame == farLeftFrame {
        cellAnimationArray.insert(cell, at: 0)
    } else if cell.frame == leftFrame {
        cellAnimationArray.insert(cell, at: 1)
    } else if cell.frame == centerFrame {
        cellAnimationArray.insert(cell, at: 2)
    } else if cell.frame == rightFrame {
        cellAnimationArray.insert(cell, at: 3)
    } else if cell.frame == farRightFrame {
        cellAnimationArray.insert(cell, at: 4)
    } else {
        print("Frame does not exist!")
        print(cell.frame)
        return
}

When I get to the line cellAnimationArray.insert(cell, at: 4), the app crashes with :

fatal error: Array index out of range

Why am I getting an out of index error when I am insert an item into the array?

@tktsubota. The way I am using the array I have to know which element is where. That is why I am using insert. — Caleb Kleveter
– Caleb Kleveter, Commented Aug 16, 2016 at 17:59
You can' insert at index 4 into an empty array. How will it know what to fill 0...3 with? — Alexander
– Alexander, Commented Aug 16, 2016 at 18:00
@AlexanderMomchliov. The issue is that, for example, index 3 is not assigned, so index 4 does not exist? — Caleb Kleveter
– Caleb Kleveter, Commented Aug 16, 2016 at 18:02
Using parallel arrays to store related data is really fragile and poor design anywy. I would consider architeching a new design. — Alexander
– Alexander, Commented Aug 16, 2016 at 18:05

Tom Harrington · Accepted Answer · 2016-08-16 18:02:58Z

6

Your error message is telling you that you're calling insert(cell, at:4) before inserting enough elements for 4 to be a valid index. Which implies that the order of items in self.cells is such that you're hitting that line before the inserts at 0 through 3. But you can't insert at 4 unless there's already something at 0 through 3.

When you use an array which already contains several items, you avoid this because index 4 is already valid.

answered Aug 16, 2016 at 18:02

Tom Harrington

71.2k12 gold badges155 silver badges175 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Array index out of range when I am inserting an element into the array

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related