What does 'Only a ReactOwner can have refs.' mean?

Question

I have a simple react component with a form in it:

var AddAppts = React.createClass({
    handleClick:          


        

Answer 1

For me the reason for the same problem was that I've imported the ReactDom globally, as a property of the window object, like this:

import ReactDOM from 'react-dom'
window.ReactDOM = ReactDOM

removing window.ReactDOM = ReactDOM fixed the problem.