How to check if IndexPath is valid?

Question

Prior to swift 3, i used to use for example:

let path = self.tableView.indexPathForSelectedRow
if (path != NSNotFound) {
//do something
 }

But now, since i use IndexPath class in swift3, i'm looking for the equivalent for the path != NSNotFound check.

Xcode8.3.1 compiler error: "Binary operator '!=' cannot be applied to operands of type 'IndexPath' and 'Int'"

Why would you check it like this? There's no way that code ever worked as-is since you can't compare `NSIndexPath` against `NSNotFound`. — rmaddy, Apr 25 '17 at 15:22
The NSIndexPath initializer simply creates an object. In what way do you expect initializing an NSIndexPath where it is 'NotFound'? This is not a query. You might be mixing it with 'indexOf', which returns an optional that can be checked for nil. — bauerMusic, Apr 25 '17 at 15:22
@bauerMusic, that was just a bad example. I was referring more to methods that return IndexPath. That would have been a better example ;) updated the question — Lirik, Apr 25 '17 at 15:32
Given your update, what's you definition of a valid index path? Is it simply whether the result is `nil` or not? — rmaddy, Apr 25 '17 at 15:37
And you really should post code that actually worked for you under Swift 2 but is now giving you trouble under Swift 3. — rmaddy, Apr 25 '17 at 15:38
I'm quite sure that `indexPathForSelectedRow` returned `nil` rather than `NSNotFound` even in Swift 2. — vadian, Apr 25 '17 at 15:50

pableiros · Answer 1 · 2021-01-16T00:46:23.547

23

To check if IndexPath exists, I use this extension function:

import UIKit

extension UITableView {

    func hasRowAtIndexPath(indexPath: IndexPath) -> Bool {
        return indexPath.section < self.numberOfSections && indexPath.row < self.numberOfRows(inSection: indexPath.section)
    }
}

And to use it I do something like this:

if tableView.hasRowAtIndexPath(indexPath: indexPath) {
    // do something
}

edited Jan 16 '21 at 00:46

answered Apr 25 '17 at 18:12

pableiros

14,932
12
99
105

Thanks for this. I think this should be in a must-included extension. – Seto Apr 10 '18 at 06:32
1

I have an NSFetchedResultsController that's returning an index path with a row index of -1. So it might be worth checking for >= 0 as well. – Murray Sagal Jan 05 '19 at 17:02
1

This gives me `EXC_BAD_ACCESS (code=1, address=0xfffffffffffffff8) numberOfRows`. My indexpath is `[-1, -1]` – Parth Jan 15 '21 at 06:31
Nevermind got the issue. The logic check is incomplete. – Parth Jan 15 '21 at 06:37

Ozgur Vatansever · Answer 2 · 2018-02-15T13:37:18.047

11

Semantically, to consider an indexPath invalid, you need something to check for such as a table view or a collection view.

Usually you can consider an indexPath invalid if it represents a row where there is no corresponding data in the data source. (One exception would be "Load more" rows.)

If you really need to create an invalid IndexPath, you can do:

let invalidIndexPath = IndexPath(row: NSNotFound, section: NSNotFound)

After the update:

self.tableView.indexPathForSelectedRow returns an Optional so can be nil if there is no selected row.

if let path = tableView.indexPathForSelectedRow {
  // There is a selected row, so path is not nil.
}
else {
  // No row is selected.
}

Anyway, comparing path against NSNotFound raises an exception in all cases.

edited Feb 15 '18 at 13:37

answered Apr 25 '17 at 15:22

Ozgur Vatansever

49,246
17
84
119

Sorry, my example was not clear. updated the example. i was referring to methods that return an indexPath. – Lirik Apr 25 '17 at 15:34
Thanks. that makes sense. – Lirik Apr 25 '17 at 15:43

Parth · Answer 3 · 2022-04-21T14:14:12.800

Improving the answer by @pableiros to handle edge case where section or row less than 0. This will happen when the table is empty and you try to access it by listOfSectionHeaders.count - 1, listOfRowsForSection.count - 1

extension UITableView {
    func isValid(indexPath: IndexPath) -> Bool {
        return indexPath.section >= 0 
            && indexPath.section < self.numberOfSections 
            && indexPath.row >= 0 
            && indexPath.row < self.numberOfRows(inSection: indexPath.section)
    }
}

score 0 · Answer 4 · answered Feb 25 '21 at 13:40

0

I stumbled on a case where collectionView(_:didEndDisplaying:forItemAt:) returns an invalid indexPath, so I used indexPath.isEmpty to check whether indexPath was indeed a row/section indexPath.

answered Feb 25 '21 at 13:40

CiNN

9,752
6
44
57

How to check if IndexPath is valid?

4 Answers4

Linked