API Reference / InstantSearch iOS Widgets / Refinement List
Apr. 24, 2019

Refinement List

About this widget

RefinementList is a filtering view that displays facets, and lets the user refine the search results by filtering on specific values.

To add a refinement list to your search experience, use these components:

  • Searcher: The Searcher that handles your searches.
  • FilterState: The current state of the filters.
  • FacetListInteractor: The logic applied to the facets.
  • FacetListController: The controller that interfaces with a concrete facet list view.
  • FacetListPresenter: Optional. The presenter that controls the sorting and other settings of the facet list view.

Examples

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let searcher: SingleIndexSearcher = SingleIndexSearcher(appID: "YourApplicationID",
                                                        apiKey: "YourSearchOnlyAPIKey",
                                                        indexName: "YourIndexName")
let filterState: FilterState  = .init()
let facetListInteractor: FacetListInteractor  = .init(selectionMode: .multiple)
let facetListController: FacetListTableViewController  = .init(tableView: UITableView())
// let facetListPresenter: FacetListPresenter = .init(sortBy: [.count(order: .descending)], limit: 5, showEmptyFacets: false)
let facetAttribute: Attribute = Attribute("facetName")

override func viewDidLoad() {
  super.viewDidLoad()
  
  facetListInteractor.connectSearcher(searcher, with: facetAttribute)
  facetListInteractor.connectFilterState(filterState, with: facetAttribute, operator: .or)
  facetListInteractor.connectController(facetListController)
  //facetListInteractor.connectController(facetListController, with: facetListPresenter)

  // Connect searcher to the filter state so that a change in the filter state triggers a new search
  searcher.connectFilterState(filterState)

  // In case we want to do a search when on empty query
  searcher.search()
  
}

Parameters

attribute
type: Attribute
Required

The attribute to filter.

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let attribute = Attribute("category")
facetListInteractor.connectSearcher(searcher, with: facetAttribute)
facetListInteractor.connectFilterState(filterState, with: facetAttribute, operator: .or)
operator
type: RefinementOperator
Required

Whether we apply an and or or behavior to the facets in the filterState.

For example if we select color as the attribute and an or behavior,
the filter sent to Algolia will be color:red OR color:green.

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facetListInteractor.connectFilterState(filterState, with: facetAttribute, operator: .or)
facetListInteractor.connectFilterState(filterState, with: facetAttribute, operator: .and)
selectionMode
type: SelectionMode
default: .multiple
Optional

Whether the list can have single or multiple selections.

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facetListInteractor = .init(selectionMode: .multiple)
facetListInteractor = .init(selectionMode: .single)

Presenter

sortBy
type: [FacetSortCriterion]
default: [.count(order: .descending)]
Optional

How to sort facets. Must be one or more of the following values:

  • .count(order: .descending)
  • .count(order: .ascending)
  • .alphabetical(order: .descending)
  • .alphabetical(order: .ascending)
  • .isRefined
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// Tie breaking algorithm where we show refined values first.
// In case of a tie, we show the facets that have the biggest counts.
// In case of a tie, we show the facets in alphabetical order.
facetListPresenter =
    FacetListPresenter(
      sortBy: [.isRefined, .count(order: .descending), .alphabetical(order: .ascending)]
    )
limit
type: Int
default: 10
Optional

The number of facet values to retrieve.

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facetListPresenter =  .init(limit: 5)
showEmptyFacets
type: Bool
default: true
Optional

Whether we show facets that have a facet count of 0.

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facetListPresenter =  .init(showEmptyFacets: false)
facetListPresenter =  .init(showEmptyFacets: true)

Customize your view

The controllers provided by default, like the FacetListTableViewController work well when you want to use native UIKit with their default behavior.

If you want to use another component such as a UICollectionView, a third-party input view, or you want to introduce some custom behavior to the already provided UIKit component, you can create your own controller conforming to the FacetListController protocol.

Protocol

var onClick: ((Facet) -> Void)?:

Closure to call when a new facet is clicked.

func setSelectableItems(selectableItems: [SelectableItem<Facet>])

Function called when a new array of selectable facets is updated. This is the UI State of the refinement list.

func reload()

Function called when we require a reload of the list view.

Example

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open class FacetListTableViewController: NSObject, FacetListController {

  public var onClick: ((Facet) -> Void)?

  public var tableView: UITableView

  var selectableItems: [RefinementFacet] = []
  var cellID: String

  public init(tableView: UITableView, cellID: String = "FacetList") {
    self.tableView = tableView
    self.cellID = cellID
    super.init()
    tableView.register(UITableViewCell.self, forCellReuseIdentifier: cellID)
    tableView.dataSource = self
    tableView.delegate = self
  }

  public func setSelectableItems(selectableItems: [RefinementFacet]) {
    self.selectableItems = selectableItems
  }

  public func reload() {
    tableView.reloadData()
  }

}

extension FacetListTableViewController: UITableViewDataSource {

  open func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return selectableItems.count
  }

  open func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: cellID, for: indexPath)

    let selectableRefinement: RefinementFacet = selectableItems[indexPath.row]

    let facetAttributedString = NSMutableAttributedString(string: selectableRefinement.item.value)
    let facetCountStringColor = [NSAttributedString.Key.foregroundColor: UIColor.gray, .font: UIFont.systemFont(ofSize: 14)]
    let facetCountString = NSAttributedString(string: " (\(selectableRefinement.item.count))", attributes: facetCountStringColor)
    facetAttributedString.append(facetCountString)

    cell.textLabel?.attributedText = facetAttributedString

    cell.accessoryType = selectableRefinement.isSelected ? .checkmark : .none

    return cell
  }

}

extension FacetListTableViewController: UITableViewDelegate {

  open func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    let selectableItem = selectableItems[indexPath.row]

    self.onClick?(selectableItem.item)
  }

}

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