UICollectionViewDropPlaceholder
A placeholder for an item dropped on a collection view.
Declaration
@MainActor class UICollectionViewDropPlaceholderOverview
When you want to insert a placeholder cell into your collection view, create a UICollectionViewDropPlaceholder object and pass it to the drop(_:to:) method of your UICollectionViewDropCoordinator. You use a placeholder cell to display a temporary interface while you load the cell’s contents asynchronously. For example, your placeholder cell might display a progress indicator or a message that the cell content isn’t yet available. The placeholder object contains the reuse identifier of the temporary cell you want to display in your collection view. It can also include a custom preview to use during the drop.
You must register the cells you use with your placeholders in advance. In your storyboard file, add a collection view cell object to your collection view, configure its appearance, set its class to UICollectionViewCell (or an appropriate subclass), and assign a reuse identifier to it. When you create your UICollectionViewDropPlaceholder object, pass the cell’s reuse identifier to init(insertionIndexPath:reuseIdentifier:). The collection view uses the information in your placeholder object to insert the cell into the collection view.
Set the cellUpdateHandler to a block of code that configures the cell as a placeholder for the incoming data.
For more information, see Supporting Drag and Drop in Collection Views.