iOS implement pagination with ReactorKit and RxSwift

Question

I'm working on a iOS project require pagination (API call will have a page parameter to pull results). The ideal is when user scroll near the bottom of collectionView, a call to API will happen to fetch more results (increase page number) then add new result to existing array of model.

Here is my implementation that work when user search:

This is PhotoListViewReactor

import RxSwift
import RxCocoa
import ReactorKit

class PhotoListViewReactor : Reactor {

  enum Action {
    case searchFlickr(_ keyword: String, _ page: Int)
  }

  enum Mutation {
    case flickrList([Photos])
  }

  struct State{
    var keyword : String?
    var photos : [Photos] = []
    var page: Int = 1
  }

  var initialState: State = State()

  init() { }

  func mutate(action: Action) -> Observable<Mutation> {
    switch action {
    case let .searchFlickr(keyword,page):
      return AppService.request(keyword: keyword,page: page)
              .catchErrorJustReturn([])
              .map{[Photos(photos: $0)]}
              .map {Mutation.flickrList($0)}
    }
  }

  func reduce(state: State, mutation: Mutation) -> State {
    var newState = state
    switch mutation {
        case let .flickrList(photos):
            newState.photos += photos
            newState.page += 1
    }


    return newState
  }

}

The function for get data from API is

static func request(keyword: String, page: Int) -> Observable<[Photo]>

I have added a page: Int to State struct but don't know how to implement page (increase page and call API when user scroll near the bottom)

Daniel T. · Accepted Answer · 2019-02-20 11:46:06Z

2

Here is a solution I wrote with RxSwift. The gist comes with both the code and unit tests. https://gist.github.com/danielt1263/10bc5eb821c752ad45f281c6f4e3034b

It handles the following:

protocol PaginationUISource {
    var reloadLastPage: Observable<Void> { get } /// reload most recently loaded page
    var loadNextPage: Observable<Void> { get } /// load next page
    var bag: DisposeBag { get }
}

protocol PaginationNetworkSource {
    associatedtype Item
    func loadData(page: Int) -> Observable<[Item]>
}

struct PaginationSink<T> {
    let isLoading: Observable<Bool> /// true if network loading is in progress.
    let elements: Observable<[T]> /// elements from all loaded pages
    let error: Observable<Error> /// fires once for each error
}

I wrote this a while ago and I think I could do better now, but it should help you get started.

edited Feb 20, 2019 at 11:46

answered Sep 26, 2018 at 15:00

Daniel T.

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3 Comments

Lê Khánh Vinh Over a year ago

thanks. let's me see how i can implement that. but trying to implement reactorKit approach. It's quite clear in the concept and can be apply with more complicate system

Daniel T. Over a year ago

I have updated the gist for Swift 4.2, and improved it.

Sunil Zalavadiya Over a year ago

@DanielT. The gist link is not exists. Can you update link?

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