Assuming you have already integrated the Scrimmage Rewards Widget into your iOS application, you can listen to
events emitted by the widget by adding a JavaScript interface to the WKWebView.

import WebKit

struct ScrimmageRewardsView: UIViewRepresentable {
  let url: URL
  let token: String

  func makeUIView(context: Context) -> WKWebView {
    // ...
    webView.load(URLRequest(url: url.appendingPathComponent("?token=\(token)")))
    // Add the JavaScript interface to handle messages with ScrimmageChannel name
    webView.configuration.userContentController.add(context.coordinator, name: "ScrimmageChannel")
    // ...
  }
  
  // Coordinator is used to handle messages from the WebView
  func makeCoordinator() -> Coordinator {
    Coordinator(self)
  }
  
  // Coordinator class
  class Coordinator: NSObject, WKNavigationDelegate, WKScriptMessageHandler {
    var parent: WebView

    init(_ parent: WebView) {
      self.parent = parent
    }

    func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {
      if message.name == "messageHandler", let body = message.body as? String {
        parent.message = body
        print("Received message from WebView: \(body)")
      }
    }
  }
}

Check out the Widget Events API for more information.