TableView Reordering index out of array

🎤 General Discussion iOS
1

I seem to not fully understand this :frowning: . I get the error, but not why I’m getting it. So if anyone could explain to me why. Perhaps I’m misunderstanding the timeline of events in iOS.

I’ve got a very simple table with two sections. The datasource looks like this:

let headerTitles = ["Playing", "Substitute"]
var currentLineup: [[Player]] = [[],[]] 

// Number of sections in table
    func numberOfSections(in tableView: UITableView) -> Int {
        return currentLineup.count
    }
    
    // Assign title to header label
    func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
        if section < headerTitles.count {
            return headerTitles[section]
        }
        return nil
    }
    
    // Number of rows in this section
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return currentLineup[section].count
    }
    
    // configure cell
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "lineupCell")
        let player = currentLineup[indexPath.section][indexPath.row] as Player
        cell?.textLabel?.text = player.name
        
        return cell!
    }
    
    // MARK: - ReOrder TableView
    
    // Can the cell be moved
    func tableView(_ tableView: UITableView, canMoveRowAt indexPath: IndexPath) -> Bool {
        if currentLineup[indexPath.section].count <= numberOfPlayersOnATeam {
            return true
        }
        return false
    }
    
    // Process the cell move
    func tableView(_ tableView: UITableView, moveRowAt fromIndexPath: IndexPath, to toIndexPath: IndexPath) {
        let playerToMove = currentLineup[fromIndexPath.section][fromIndexPath.row]
        currentLineup[fromIndexPath.section].remove(at: fromIndexPath.row)
        currentLineup[fromIndexPath.section].insert(playerToMove, at: toIndexPath.row)
    }

So when my table renders it has two sections with 4 players in each section.

Section 1
Player 1
Player 2
Player 3
Player 4
Section 2
Player 5
Player 6
Player 7
Player 8

If I move a player 4 into section 2 right at the bottom, after player 8, it will crash and say index out of array. I understand what the error says, but not why I get it. I want to insert player 4 into that array. So what’s issue? I have also tried changing the insert() line to this currentLineup[fromIndexPath.section].insert(playerToMove, at: 0)

This I hoped would mean that every row moved between sections was inserted at position 0 and therefore alleviate this error. So what am I missing here? And what is the the accepted iOS way to deal with this problem?

2

I think the last line in the code is wrong:

    currentLineup[fromIndexPath.section].insert(playerToMove, at: toIndexPath.row)

should be

    currentLineup[toIndexPath.section].insert(playerToMove, at: toIndexPath.row)

so that you tell it the section and row to move to.

1 Like
3

Thanks @sgerrard - A silly error on my part. But a quick fix, so i’ll take that!