CODEWITHSUNDEEP
iosswiftuicollectionview
Peter A. Kolski
Peter A. Kolski

Reputation: 69

Delete specific items in UICollectionView

I want to delete cells in a UICollectionView, which have a certain ID. So the cell can be in the middle of the view.

To do so I remove the item from my cell array and also remove the indexPath. The indexPath has to be retrieved first. This is not possible!

Somehow the cells which are not visible / hidden (below the current view, have to be scrolled up) can not be deleted, as they turn out to be NIL.

How can I access a certain cell (with an ID) and delete it?

    let cellIdToFeedItem_ToDelete = [ String : FeedItem ]() // here are the item to be deleted
    var indexPathsToRemove        = [ IndexPath ]()
    var indexPathsAllActive       = [ IndexPath ]() // Will be filled below

    // --- retrieving all indexPaths
    if let nrSections = self.collectionView?.numberOfSections
    {
        for s in 0..<nrSections
        {
            if let v = self.collectionView?.numberOfItems( inSection: s )
            {
                for i in 0..<v
                {
                    let indexPathTMP = IndexPath( item: i, section: s )
                    indexPathsAllActive.append( indexPathTMP )
                }
            }
        }
    }

    // --- delete the items with the same
    for indexPath in indexPathsAllActive
    {
        // #### FOR HIDDEN CELLS THIS IS 'NIL'
        let cell = self.collectionView?.cellForItem( at: indexPath ) as? FeedCollectionViewCell

        if let cellID = cell?.id
        {
            if let _ = cellIdToFeedItem_ToDelete[ cellID ]
            {
                if let index = feedItemsActive_.firstIndex( where: {
                    (i) -> Bool in
                    i.id == cellID
                } )
                {
                    feedItemsActive_.remove( at: index )
                    indexPathsToRemove.append( indexPath )
                }
            }
        }
    }

    self.collectionView?.deleteItems( at: indexPathsToRemove )

Upvotes: 0

Views: 458

Answers (2)

ahbou
ahbou

Reputation: 4918

Remove the items from your datasource (indexPathsAllActive I assume?) then reload your collectionView to show the changes.

Without animation:

collectionView.reloadData()

With animations:

collectionView.performBatchUpdates{ }

Here's how you'd use performBatchUpdates with your code: (If you have one section)

collectionView?.performBatchUpdates({
    var targetIndexPaths: [IndexPath] = []
    for ( cellID, _ ) in cellIdToFeedItem_ToDelete
    {
        if let index = feedItemsActive_.firstIndex( where: { $0.id == cellID } )
        {
            feedItemsActive_.remove( at: index )
            targetIndexPaths.append(IndexPath(item: index, section: 0))
        }
    }
    collectionView?.deleteItems(at: targetIndexPaths]) 
}, completion: nil)

Upvotes: 3

Peter A. Kolski
Peter A. Kolski

Reputation: 69

This did the job. But without animation though:

    for ( cellID, _ ) in cellIdToFeedItem_ToDelete
    {
        if let index = feedItemsActive_.firstIndex( where: {
            (i) -> Bool in
            i.id == cellID
        } )
        {
            feedItemsActive_.remove( at: index )
        }
    }

    self.collectionView?.reloadData()

Upvotes: 0

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