/* solution 1 */
onSubmit(data) {
  Promise.resolve(this.props.submit(data)).then(
    (result) => this.setState({ result: result })
  )
}

/* solution 2 */
onSubmit(data) {
  const result = this.props.submit(data)
  
  if (prom instanceof Promise) {
    result.then((promise_result) => {
      this.setState({ result: promise_result })
    })
  } else {
    this.setState({ result: result })
  }
}