Concepts / Building Search UI / Create your own widgets
Aug. 21, 2019

Create Your Own Widgets

If none of the existing widgets fit your use-case, you could implement your own widget.

Introduction

You are trying to create your own widget with InstantSearch iOS and that’s awesome 🎉. But that also means that you couldn’t find the widgets or built-in options you were looking for. We’d love to hear about your use case as our mission with our InstantSearch libraries is to provide the best out-of-the-box experience. Don’t hesitate to send us a quick message explaining what you were trying to achieve either using the form at the end of that page or directly by submitting a feature request

Overview

Creating a widget takes three steps:

  • Create the MyWidgetInteractor, containing the business logic for your widget.
  • Create a MyWidgetController interface, describing the rendering of the widget data.
    • Implement it in a MyConcreteWidgetController that you will use.
  • Create the connection methods between your Interactor and every other component:
    • Create a connectController() to connect your Interactor to its Controller.
    • If it uses the Searcher, a connectSearcher().
    • If it uses the FilterState, a connectFilterState().

Example

We will build a widget that displays the number of searches made since it was last clicked.

Create the Interactor

Our Interactor will be quite straightforward: it stores a sum that can be incremented or reseted to 0. We will use InstantSearch’s Observer to allow subscribing to changes of the sum’s value.

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class SumSearchesInteractor {

  var sum: Int = 0 {
    didSet {
      onSumChanged.fire(sum)
    }
  }

  public let onSumChanged: Observer<Int> = .init()

  func increment() {
    sum += 1
  }

  func reset() {
    sum = 0
  }

}

Create the Controller interface

To interact with the data in our ViewModel, we need a view than can display a number, and handle clicks to reset the counter.

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protocol SumSearchesController {
    func setSum(sum: Int) // will be called on new sum
    var onReset: (() -> Void)? { get set } // will hold the callback to reset the sum
}

Implementing our Controller

We can now implement a SumSearchesButtonController: it should display the data received in setSum and trigger onReset when clicked.

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class SumSearchesButtonController : SumSearchesController {

  let button: UIButton
  var onReset: (() -> Void)?

  init(button: UIButton) {
    self.button = button
    button.addTarget(self, action: #selector(didPressButton), for: .touchUpInside)
  }

  func setSum(sum: Int) {
    button.setTitle("\(sum)", for: .normal)
  }

  @objc func didPressButton() {
    onReset?()
  }

}

Create the connectController method

To link our Interactor and its Controller(s), we’ll define a connection method to describe what should happen when we connect them (subscribe to sum and set the reset callback). We can do this in the Interactor’s extension.

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extension SumSearchesInteractor {

  func connectController<Controller: SumSearchesController>(_ controller: Controller) {
    onSumChanged.subscribePast(with: self) { (interactor, sum) in
      controller.setSum(sum: sum)
    }

    controller.onReset = { [weak self] in
      self?.reset()
    }
  }

}

Create the connectSearcher method

Because our widget needs to be aware of searches to count them, it needs to be connected to a Searcher.

We’ll subscribe to the Searcher’s onResults, and call increment() on every new search response.

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extension SumSearchesInteractor {

  func connectSearcher(_ searcher: SingleIndexSearcher) {
    searcher.onResults.subscribe(with: self) { (interactor, _) in
      interactor.increment()
    }
  }

}

Putting it all together

You just created your first custom widget, congratulations! 🎉

Now you can use your widget in your application, like any other widget:

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// Initialize your Searcher as usual
let searcher = SingleIndexSearcher(appID: "YourApplicationID",
				   apiKey: "YourSearchOnlyAPIKey",
				   indexName: "YourIndexName")


// Create your Interactor and Controller implementation
let sumSearchesInteractor = SumSearchesInteractor()
let sumSearchesButton = UIButton()
let sumSearchesButtonController = SumSearchesButtonController(button: sumSearchesButton)

// Connect your Interactor to start displaying the count of searches
sumSearchesInteractor.connectSearcher(searcher)
sumSearchesInteractor.connectController(sumSearchesButtonController)

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