Reason React Native: Workaround to get jsThis from Reason-React

example.re

module Example {
  type jsProps = {. x: int, y: string };

  type state = ReasonReact.stateless;
  type props = ReasonReact.noRetainedProps;
  type action = ReasonReact.actionless;

  let component = ReasonReact.statelessComponent("Example");
  
  let make = (jsThis: Withjs.thisType) => (~x, ~y) => (_children) => {
    /* ... */
    let onPress = () => eventuallyCall_findNodeHandle(jsThis);
    /* ... */
    {
      ...component,
      render: (_self) => {
        <TouchableHighlight onPress=onPress>
          <Text value="Hello world" />
        </TouchableHighlight>
      }
    }
  };
};

include Withjs.Make(Example);

withjs.re

type thisType = unit;

module type Component = {
  type jsProps;

  type state;
  type props;
  type action;

  let component: ReasonReact.component(state, props, action);
  let jsPropsToReason: (thisType) => ReasonReact.jsPropsToReason(jsProps, state, props, action);
};

module Make = (C : Component) => {
  let _mutJsThis: ref(option(thisType)) = ref(None);

  let injectThis = (this) => { _mutJsThis := Some(this); };

  exception Not_wrapped;

  let jsComponentFactory = () => switch _mutJsThis^ {
    | None => raise(Not_wrapped)
    | Some(jsThis) => ReasonReact.wrapReasonForJs(
        ~component=C.component,
        C.jsPropsToReason(jsThis)
      );
  };
};

withreason.js

const withReason: ((any) => void, () => React.ComponentType<any>) => React.ComponentType<any> = (injectThis, componentFactory) => {
  return class ReasonableComponent extends React.Component<any> {
    Component: React.ComponentType<any>;

    constructor(props) {
      super(props);
      injectThis(this);
      this.Component = componentFactory();
    }

    render() {
      const Component = this.Component;
      return <Component {...this.props}/>;
    }
  }
}

//
// Usage: Use the HoC to use the Reason component from JS
//

import { jsComponentFactory, injectThis } from './lib/js/example.js'

export default withReason(injectThis, jsComponentFactory);