Drag & Drop UITableViewDropDelegate

drag-drop-uitableviewdropdelegate.swift

extension BoardCollectionViewCell: UITableViewDropDelegate {
    
    func tableView(_ tableView: UITableView, performDropWith coordinator: UITableViewDropCoordinator) {
        if coordinator.session.hasItemsConforming(toTypeIdentifiers: [kUTTypePlainText as String]) {
            coordinator.session.loadObjects(ofClass: NSString.self) { (items) in
                guard let string = items.first as? String else {
                    return
                }
                var updatedIndexPaths = [IndexPath]()
                
                switch (coordinator.items.first?.sourceIndexPath, coordinator.destinationIndexPath) {
                case (.some(let sourceIndexPath), .some(let destinationIndexPath)):
                    // Same Table View
                    if sourceIndexPath.row < destinationIndexPath.row {
                        updatedIndexPaths =  (sourceIndexPath.row...destinationIndexPath.row).map { IndexPath(row: $0, section: 0) }
                    } else if sourceIndexPath.row > destinationIndexPath.row {
                        updatedIndexPaths =  (destinationIndexPath.row...sourceIndexPath.row).map { IndexPath(row: $0, section: 0) }
                    }
                    self.tableView.beginUpdates()
                    self.board?.items.remove(at: sourceIndexPath.row)
                    self.board?.items.insert(string, at: destinationIndexPath.row)
                    self.tableView.reloadRows(at: updatedIndexPaths, with: .automatic)
                    self.tableView.endUpdates()
                    break
                    
                case (nil, .some(let destinationIndexPath)):
                    // Move data from a table to another table
                    self.removeSourceTableData(localContext: coordinator.session.localDragSession?.localContext)
                    self.tableView.beginUpdates()
                    self.board?.items.insert(string, at: destinationIndexPath.row)
                    self.tableView.insertRows(at: [destinationIndexPath], with: .automatic)
                    self.tableView.endUpdates()
                    break
                    
                    
                case (nil, nil):
                    // Insert data from a table to another table
                    self.removeSourceTableData(localContext: coordinator.session.localDragSession?.localContext)
                    self.tableView.beginUpdates()
                    self.board?.items.append(string)
                    self.tableView.insertRows(at: [IndexPath(row: self.board!.items.count - 1 , section: 0)], with: .automatic)
                    self.tableView.endUpdates()
                    break
                    
                default: break
                    
                }
            }
        }
    }
    
    func removeSourceTableData(localContext: Any?) {
        if let (dataSource, sourceIndexPath, tableView) = localContext as? (Board, IndexPath, UITableView) {
            tableView.beginUpdates()
            dataSource.items.remove(at: sourceIndexPath.row)
            tableView.deleteRows(at: [sourceIndexPath], with: .automatic)
            tableView.endUpdates()
        }
    }
    
    func tableView(_ tableView: UITableView, dropSessionDidUpdate session: UIDropSession, withDestinationIndexPath destinationIndexPath: IndexPath?) -> UITableViewDropProposal {
        return UITableViewDropProposal(operation: .move, intent: .insertAtDestinationIndexPath)
    }
    
}