Xstate Cannot set property '_sessionid' of undefined

Question

I'm trying to create an interpret for Xstate, and I'm trying to pass it a Machine I had created in a separate file, something like this:

    import { Machine } from 'xstate';

    const testMachine = Machine({
    id: 'testMachine',
    initial: 'start',
    states: {
    start: {
      on: {
        PUB_TOPIC: 'wait_micro_res',
      },

    },
    wait_micro_res: {
      on: {
        MACHINE_DISCONNECTED: 'disconnection',
        CONFIRMATION_RECEIVED: 'wait_order',
      },
    },
    wait_order: {
      on: {
        DISCONNECTION_ORDER: 'end',
        EXPERIMENT_ORDER: 'wait_measurement',
      },
    },
    wait_measurement: {
      on: {
        EXPERIMENT_FINISHED: 'end',
        MEASUREMENT_RECEIVED: 'receive_measurement',
      },
    },
    receive_measurement: {
      on: {
        SEND_2_EXPERIMENT_MS: 'wait_measurement',
      },
    },
    disconnection: {
      on: {
        RECONNECTION: 'wait_micro_res',
      },
    },
    end: {
      type: 'final',
    },
    },
    });

     export default {
     testMachine,
     };

I'm trying to create it this way:

import { interpret } from 'xstate/lib/interpreter';
import testMachine from '../stateMachine/index';

const machineService = interpret(testMachine)
      .onTransition((state) => {
        console.log(state.value);
      })
      .start();

However I'm getting this error:

TypeError: Cannot set property '_sessionid' of undefined

When I try to create the machine in the same file of the interpreter all runs fine. I tried to log the machine and it seems to be imported correctly, but I don't know if there's an additional mistake I'm not aware about

Answer 1

There seems to be a problem with your export. You are exporting { testMachine } as the default export instead of testMachine.

You should use:

export default testMachine;

Then when you import testMachine from '../stateMachine/index'; you will get the desired object.

For now you are importing an object with a property testMachine that contains you machine. If you want to keep that export, use:

const machineService = interpret(testMachine.testMachine)