> ## Documentation Index
> Fetch the complete documentation index at: https://algolia.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Hierarchical Menu
> Shows a hierarchical menu to navigate nested categories.
export const FlavorSwitcher = ({current, baseHref = "", options = [], label = "InstantSearch framework"}) => {
if (options.length === 0) {
return
FlavorSwitcher requires at least one option.
;
}
const selected = options.find(option => option.value === current) ?? options[0];
return ;
};
```swift Signature theme={"system"}
HierarchicalConnector(
searcher: SingleIndexSearcher,
filterState: FilterState,
hierarchicalAttributes: [Attribute],
separator: String,
controller: HierarchicalController,
presenter: HierarchicalPresenter
)
```
Browse the Hierarchical Menu example code on GitHub.
## About this widget
A `Hierarchical Menu` is a component that displays a hierarchical navigation menu, based on facet attributes.
## Examples
Instantiate a `HierarchicalConnector` and launch an initial search on its [`Searcher`](/doc/api-reference/widgets/instantsearch/ios).
```swift Swift icon=code theme={"system"}
let searcher = HitsSearcher(appID: "YourApplicationID",
apiKey: "YourSearchOnlyAPIKey",
indexName: "YourIndexName")
let filterState: FilterState = .init()
searcher.connectFilterState(filterState)
let hierarchicalAttributes: [Attribute] = [
"categories.lvl0",
"categories.lvl1",
"categories.lvl2",
]
let hierarchicalTableViewController: HierarchicalTableViewController = .init(tableView: UITableView())
let hierachicalConnector: HierarchicalConnector = .init(searcher: searcher,
filterState: filterState,
hierarchicalAttributes: hierarchicalAttributes,
separator: " > ",
controller: hierarchicalTableViewController,
presenter: DefaultPresenter.Hierarchical.present)
searcher.search()
```
## Parameters
The [`Searcher`](/doc/api-reference/widgets/instantsearch/ios) that handles your searches.
The [`FilterState`](/doc/api-reference/widgets/filter-state/ios) that holds your filters.
The names of the hierarchical attributes to target, in ascending order.
The delimiter used to separate hierarchical facets.
Usually something like " > ", including spaces as shown in this example.
The Controller interfacing with a concrete hierarchical view.
The Presenter defining how hierarchical facets appear in the controller.
## Presenter
The presenter defining how to display the `HierarchicalFacet` list.
Takes a list of `HierarchicalFacet` as input and returns a new `HierarchicalFacet` list.
A `HierarchicalFacet` is a tuple of a `Facet`, its `level`, and whether it's `selected` or not.
```swift Swift icon=code theme={"system"}
public static let present: HierarchicalPresenter = { facets in
let levels = Set(facets.map { $0.level }).sorted()
guard !levels.isEmpty else { return facets }
var output: [HierarchicalFacet] = []
output.reserveCapacity(facets.count)
levels.forEach { level in
let facetsForLevel = facets
.filter { $0.level == level }
.sorted { $0.facet.value < $1.facet.value }
let indexToInsert = output
.lastIndex { $0.isSelected }
.flatMap { output.index(after: $0) } ?? output.endIndex
output.insert(contentsOf: facetsForLevel, at: indexToInsert)
}
return output
}
```
## Low-level API
If you want to fully control the `Hierarchical Menu` components and connect them manually, you can use the following components:
* `Searcher`. The [`Searcher`](/doc/api-reference/widgets/instantsearch/ios) that handles your searches.
* `FilterState`. The current state of the filters.
* `HierarchicalInteractor`. The logic applied to the hierarchical facets.
* `HierarchicalController`. The controller that interfaces with a concrete hierarchical facet list view.
* `HierarchicalPresenter`. Optional. The presenter that controls the sorting and other settings of the refinement facet list view.
```swift Swift icon=code theme={"system"}
let searcher = HitsSearcher(appID: "YourApplicationID",
apiKey: "YourSearchOnlyAPIKey",
indexName: "YourIndexName")
let filterState: FilterState = .init()
let hierarchicalAttributes: [Attribute] = [
"categories.lvl0",
"categories.lvl1",
"categories.lvl2",
]
let hierarchicalTableViewController: HierarchicalTableViewController = .init(tableView: UITableView())
let hierarchicalInteractor: HierarchicalInteractor = .init(hierarchicalAttributes: hierarchicalAttributes,
separator: " > ")
searcher.connectFilterState(filterState)
hierarchicalInteractor.connectSearcher(searcher: searcher)
hierarchicalInteractor.connectFilterState(filterState)
hierarchicalInteractor.connectController(hierarchicalTableViewController)
searcher.search()
```
## Customizing your view
The default controllers, for example, `HierarchicalTableViewController`,
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 `HierarchicalController` protocol.
### Protocol
`var onClick: ((String) -> Void)?`:
Closure to call when a new hierarchical facet is clicked.
`func setItem(_ item: [HierarchicalFacet])`
Function called when a new array of hierarchical facets is updated. This is the UI State of the refinement list. Make sure to reload your view here when you get the new items.
### Example
```swift Swift icon=code theme={"system"}
open class HierarchicalTableViewController: NSObject, HierarchicalController {
public var onClick: ((String) -> Void)?
var items: [HierarchicalFacet]
var tableView: UITableView
let cellID: String
public init(tableView: UITableView, cellID: String = "HierarchicalFacet") {
self.tableView = tableView
self.items = []
self.cellID = cellID
super.init()
tableView.register(UITableViewCell.self, forCellReuseIdentifier: cellID)
tableView.dataSource = self
tableView.delegate = self
}
public func setItem(_ item: [HierarchicalFacet]) {
self.items = item
tableView.reloadData()
}
}
extension HierarchicalTableViewController: UITableViewDataSource {
open func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return items.count
}
open func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: cellID, for: indexPath)
let maxSelectedLevel = Set(items.filter { $0.isSelected }.map { $0.level }).max() ?? 0
let item = items[indexPath.row]
cell.textLabel?.text = "\(item.facet.description)"
cell.indentationLevel = item.level
cell.accessoryType = item.level == maxSelectedLevel && item.isSelected ? .checkmark : .none
return cell
}
}
extension HierarchicalTableViewController: UITableViewDelegate {
open func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
let item = items[indexPath.row]
onClick?(item.facet.value)
}
}
```
### SwiftUI
InstantSearch provides the `HierarchicalList` SwiftUI view which you can embed in your views.
It uses `HierarchicalObservableController` as a data model,
which is an implementation of the `HierarchicalController` protocol adapted for usage with SwiftUI.
`HierarchicalObservableController` must be connected to the `HierarchicalConnector` or `HierarchicalInteractor` like any other `HierarchicalController` implementation.
You can define the appearance of the view representing a single hierarchical facet and its selection state or use the `HierarchicalFacetRow` view provided by InstantSearch.
```swift Swift icon=code theme={"system"}
struct ContentView: View {
@ObservedObject let hierarchicalController: HierarchicalObservableController
var body: some View {
HierarchicalList(hierarchicalController) { facet, nestingLevel, isSelected in
// Use the implementation provided by InstantSearch
// HierarchicalFacetRow(facet: facet,
nestingLevel: nestingLevel,
isSelected: isSelected)
// Or declare a custom single hierarchical facet view
HStack(spacing: 10) {
Image(systemName: isSelected ? "chevron.down" : "chevron.right")
.font(.callout)
Text("\(facet.value) (\(facet.count))")
.fontWeight(isSelected ? .semibold : .regular)
.contentShape(Rectangle())
Spacer()
}
.padding(.leading, CGFloat(nestingLevel * 20))
}
}
}
```
If you prefer to create a custom SwiftUI view that presents the list of hierarchical facets,
you can directly use the `HierarchicalObservableController` as a data model.
It provides the `hierarchicalFacets` property along with the `toggle` function to streamline the design process of your custom SwiftUI view.