API Reference / InstantSearch iOS Widgets / Filter List (Numeric)
Widget signature
NumericFilterListConnector(
  numericFilters: [NumericFilter],
  selectionMode: SelectionMode,
  filterState: FilterState,
  operator: RefinementOperator,
  groupName: String,
  controller: FilterListTableController<Filter.Numeric>
)

About this widget

NumericFilterList is a filtering component that displays numeric filters and lets the user refine the search results by selecting them.

Compared to the RefinementList, which takes its values from the search response facets, this widget displays numeric filters that you add yourself.

Examples

Instantiate a NumericFilterListConnector and launch an initial search on its Searcher.

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let searcher: SingleIndexSearcher = SingleIndexSearcher(appID: "YourApplicationID",
                                                        apiKey: "YourSearchOnlyAPIKey",
                                                        indexName: "YourIndexName")

let filterState = FilterState()

let filters: [Filter.Numeric] = [
  .init(attribute: "price", operator: .lessThan, value: 5),
  .init(attribute: "price", range: 5...10),
  .init(attribute: "price", range: 10...25),
  .init(attribute: "price", range: 25...100),
  .init(attribute: "price", operator: .greaterThan, value: 100)
]

let filterListTableView: UITableView = .init()
let filterListController: FilterListTableController<Filter.Numeric> = .init(tableView: filterListTableView)

let filterListConnector = NumericFilterListConnector(numericFilters: filters,
                                                     selectionMode: .multiple,
                                                     filterState: filterState,
                                                     operator: .and,
                                                     groupName: "Numeric Filters",
                                                     controller: filterListController)

searcher.connectFilterState(filterState)
searcher.search()

Parameters

numericFilters
type: [NumericFilter]
default: []
Required

The numeric filters to display.

selectionMode
type: SelectionMode
default: .single
Optional

Whether a user can select .single or .multiple values.

filterState
type: FilterState
Required

The FilterState that holds your filters.

operator
type: RefinementOperator
Required

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

For example if we have an or behavior, the filter sent to Algolia will be _tags:promo OR color:green.

groupName
type: String
Required

Filter group name.

controller
type: FilterListTableController<Filter.Numeric>
default: nil
Optional

Controller interfacing with a concrete filter list view.

Low-level API

If you want to fully control the NumericFilterList components and connect them manually, use the following components:

  • Searcher: The Searcher that handles your searches.
  • FilterState: The current state of the filters.
  • NumericFilterListInteractor: The logic applied to the numeric filters.
  • FilterListController: The view that will render the numeric filters.
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let searcher: SingleIndexSearcher = SingleIndexSearcher(appID: "YourApplicationID",
                                                        apiKey: "YourSearchOnlyAPIKey",
                                                        indexName: "YourIndexName")

let filterState = FilterState()

let filters: [NumericFilter] = [
  .init(attribute: "price", operator: .lessThan, value: 5),
  .init(attribute: "price", range: 5...10),
  .init(attribute: "price", range: 10...25),
  .init(attribute: "price", range: 25...100),
  .init(attribute: "price", operator: .greaterThan, value: 100)
]


let filterListInteractor = NumericFilterListInteractor(items: filters,
                                                       selectionMode: .multiple)

filterListInteractor.connectFilterState(filterState,
                                        operator: .and,
                                        groupName: "Numeric Filters")
  
searcher.connectFilterState(filterState)
searcher.search()

Customizing your view

The default controllers, e.g., FilterListTableController, 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 NumericFilterListController protocol.

Protocol

var onClick: ((Filter.Numeric) -> Void)?:

Closure to call when a filter is clicked.

func setSelectableItems(selectableItems: [SelectableItem<Filter.Numeric>])

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.

Implementation example

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class NumericFilterListTableController: NSObject, NumericFilterListController, UITableViewDataSource, UITableViewDelegate {
  
  public var onClick: ((Filter.Numeric) -> Void)?
  
  public let tableView: UITableView
  
  public var selectableItems: [SelectableItem<Filter.Numeric>] = []
  public var filterPresenter: FilterPresenter?
  
  let cellID: String
  
  public init(tableView: UITableView, cellID: String = "cellID") {
    self.tableView = tableView
    self.cellID = cellID
    super.init()
    tableView.dataSource = self
    tableView.delegate = self
    tableView.register(UITableViewCell.self, forCellReuseIdentifier: cellID)
  }
  
  // MARK: - FilterListController
  
  public func setSelectableItems(selectableItems: [SelectableItem<Filter.Numeric>]) {
    self.selectableItems = selectableItems
  }
  
  public func reload() {
    tableView.reloadData()
  }
  
  // MARK: - UITableViewDataSource
  
  func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return selectableItems.count
  }
  
  func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: cellID, for: indexPath)
    let filter = selectableItems[indexPath.row]
    let filterPresenter = self.filterPresenter ?? DefaultPresenter.Filter.present
    cell.textLabel?.text = filterPresenter(Filter(filter.item))
    cell.accessoryType = filter.isSelected ? .checkmark : .none
    
    return cell
  }
  
  // MARK: - UITableViewDelegate
  
  func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    let selectableItem = selectableItems[indexPath.row]
    onClick?(selectableItem.item)
  }
  
}

SwiftUI

InstantSearch provides the FilterList SwiftUI view which you can embed in your views. It uses FilterListObservableController as a data model, which is an implementation of the SelectableListController protocol adapted for usage with SwiftUI. FilterListObservableController must be connected to the NumericFilterListConnector or NumericFilterListInteractor like any other SelectableListController implementation. You have to define the appearance of the view representing a single numeric filter and its selection state.

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struct ContentView: View {

  @ObservedObject var filterListController: FilterListObservableController<Filter.Numeric>

  var body: some View {
    FilterList(filterListController) { filter, isSelected in
      // declare the view presenting a single numeric filter and its selection state
      HStack {
        Text(filter.description)
        Spacer()
        if isSelected {
          Image(systemName: "checkmark")
            .foregroundColor(.accentColor)
        }
      }
      .contentShape(Rectangle())
      .frame(idealHeight: 44)
      .padding(.horizontal, 5)
    }
  }
}

If you prefer to create a custom SwiftUI view that presents the list of numeric filters, you can directly use the FilterListObservableController<Filter.Numeric> as a data model. It provides filters and selections properties along with toggle and isSelected functions to streamline the design process of your custom SwiftUI view.

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