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items = collectionActions.scan([], accumulator: { (currentBooks, action) -> [Book] in
    switch action {
    case .bookMarkedForDeletion(let book):
        return currentBooks.filter { $0 != book }
    case .collectionRefreshed(withBooks: let books):
        return books
    }
})

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let collectionActions = ReplaySubject<BookCollectionAction>.create(bufferSize: 1)

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enum BookCollectionAction {
    case collectionRefreshed(withBooks: [Book])
    case bookMarkedForDeletion(_ book: Book)
}

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tableView.rx.itemDeleted
    .bind(to: viewModel.deleteCommand)
    .disposed(by: disposeBag)

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import UIKit
import RxDataSources
import RxSwift

class ViewController: UIViewController {

    @IBOutlet weak var tableView: UITableView!
    let dataSource = createDataSource()
    let disposeBag = DisposeBag()

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struct SectionOfBooks {
    var header: String?
    var items: [Book]
}

func createDataSource() -> RxTableViewSectionedAnimatedDataSource<SectionOfBooks> {
    return RxTableViewSectionedAnimatedDataSource(
        configureCell:{ (ds, tableView, indexPath, book) in
            let cell = tableView.dequeueReusableCell(...)
            cell.textLabel?.text = book.title

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deleteCommand
    .map { $0.row }
    .withLatestFrom(items) { rowIndex, items in
        return items[rowIndex]
    }.flatMap(api.deleteBook)
    .subscribe()
    .disposed(by: disposeBag)

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deleteCommand
    .map { $0.row }
    .withLatestFrom(items) { rowIndex, items in
        return items[rowIndex]
    }

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deleteCommand
    .map { $0.row }
    // convert Int (position) into element of books collection
    // pass it to API method

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import RxSwift
import RxCocoa

class BooksViewModel {
    // MARK: inputs
    let deleteCommand = PublishRelay<IndexPath>()

    // MARK: outputs
    let items: Observable<[Book]>