Form.js

import React from 'react';
import { Form } from 'react-final-form';

export default ({ render, transform, ...rest })=> <Form
  {...rest}
  render={({ values, ...renderPropsRest }) => render({ values: transform(values), ...renderPropsRest })}
/>;

// the function passed to transform is x => MyModelSubclass.getFromCache(x)

export default class Model {
  /**
   * What are we doing here?
   * We are stringifying an object, then storing the Model
   * version of that in a cache. That way, we can avoid re-creating
   * it later when we have the same object.
   */
  static cache = {};
  static getFromCache(obj) {
    const stringified = JSON.stringify(obj);
    if (!this.cache[stringified]) {
      const Constructor = this;
      this.cache[stringified] = new Constructor(obj);
    }
    return this.cache[stringified];
  };
}