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

There is another situation.

I set the React as external library in the webpack.config.js and import react.js from cdnjs.

externals: {
  'react': 'React'
}

When I using an ui library depend on React,such as material-ui,react-bootstrap,this issue occurred.