Observable Proxy instance

[Joozty]

I am trying to connect my proxy class with MobX. My use case is that I need to validate/convert the value before it's added to object. However, when I run my code, set trap is never called. Obviously, the value is changing correctly but I need to covert the case for example when the user assigns a string and that string should be converted to a number in set trap. Is there any way to make it work with MobX. Any help is appreciated. Thanks a lot. :)

import React from "react";
import { observer } from "mobx-react-lite";
import { observable, extendObservable, configure } from "mobx";

configure({ enforceActions: false }); // strict mode

class Store {
  constructor() {
    this.params = observable(
      new Proxy(
        {},
        {
          set: (object, key, value) => {
            alert("set: ", key, value);
            // validate and convert value <==============
            object[key] = value;
            return true;
          },
          get: (object, key) => {
            console.log("get: ", key);
            if (typeof object[key] === "function")
              return (...args) => Reflect.apply(object[key], object, args);

            return object[key];
          }
        }
      )
    );

    extendObservable(this.params, { value: 0 });
  }
}

const store = new Store();

const App = observer(() => (
  <>
    <div>Value: {store.params.value}</div>

    <button onClick={() => (store.params.value++)}>increment</button>
  </>
));

export default App;

Codesandbox here

[urugator]

You have to do it other way around this.params = new Proxy(observable({}))
Calling extendObservable on proxy could be a bit tricky, not sure.
If I may suggest, don't use proxy for this, keep validation inside action that adds the value to the object.