RXSwift - RxCollectionViewSectionedReloadDataSource - Drag & drop move (Reorder) - ios

Question

I have used RxCollectionViewSectionedReloadDataSource to load my data into UICollectionView.
let dataSource = RxCollectionViewSectionedReloadDataSource<SectionModel<String, WorkGroup>>(
configureCell: { (_, collectionView, indexPath, item) in
guard let cell = collectionView
.dequeueReusableCell(withReuseIdentifier: WorkGroupCell.identifier, for: indexPath) as? WorkGroupCell else {
return WorkGroupCell()
}
cell.viewModel = item
return cell
}
)
viewModel.items.bind(to: tileCollectonView.rx.items(dataSource: dataSource)).disposed(by: disposeBag)
tileCollectonView.rx.setDelegate(self).disposed(by: disposeBag)
Using above code i can display the data. But i want to drag and drop(Reorder) the cell.
Please let me know how can i do that reorder using RxSwift.
Help will be highly appreciated.

Answer 1

As is often the case, you need a state machine.
The logic involved is quite simple:
struct State<Item> {
var items: [Item] = []
}
func state<Item>(initialState: State<Item>, itemMoved: Observable<ItemMovedEvent>) -> Observable<State<Item>> {
itemMoved
.scan(into: initialState) { (state, itemMoved) in
state.items.move(from: itemMoved.sourceIndex.row, to: itemMoved.destinationIndex.row)
}
.startWith(initialState)
}
extension Array
{
mutating func move(from oldIndex: Index, to newIndex: Index) {
if oldIndex == newIndex { return }
if abs(newIndex - oldIndex) == 1 { return self.swapAt(oldIndex, newIndex) }
self.insert(self.remove(at: oldIndex), at: newIndex)
}
}
The above uses the ItemMovedEvent provided by RxCocoa for table views. In order to create something like that for a collection view, you will need to wrap the UICollectionViewDragDelegate in a delegate proxy. An article on how to do that can be found here: Convert a Swift Delegate to RxSwift Observables