Nested states for the payment authorisation state machine described in my blog post: https://medium.com/@sdavico/integrate-xstate-with-react-native-and-react-navigation-21ead87391da

keychainAccessStates.js

import { Machine, send, assign, actions } from "xstate";

const { choose, log } = actions;

const keychainAccessStates = {
  initial: "checkingBiometricFactor",
  states: {
    checkingBiometricFactor: {
      on: {
        RETRY: { target: "checkingBiometricFactor", internal: false },
        STOP_TRYING: { target: "biometricAttemptsFinished" },
        // prevent transitions from "checkingBiometricFactor"
        KEYCHAIN_ACCESS_OK: undefined,
        KEYCHAIN_ACCESS_KO: undefined,
      },
      invoke: {
        id: "checkingBiometricFactor",
        src: "checkingBiometricFactor",
        onDone: {
          target: "biometricSuccess",
        },
        onError: {
          actions: [
            assign((ctx) => ({
              authAttempts: ctx.authAttempts + 1,
            })),
            choose([
              {
                cond: (ctx) => ctx.authAttempts > 3,
                actions: [
                  log("attempts finished"),
                  send("STOP_TRYING"),
                ],
              },
              {
                // else
                actions: [log("retrying..."), send("RETRY")],
              },
            ]),
          ],
        },
      },
    },
    biometricSuccess: {
      type: "final",
      entry: [
        log("reporting ok to parent state"), 
        send("KEYCHAIN_ACCESS_OK")],
    },
    biometricAttemptsFinished: {
      type: "final",
      entry: [
        log("reporting ko to parent state"),
        send("KEYCHAIN_ACCESS_KO"),
      ],
    },
  },
};