React refs example

class Parent extends React.Component {
   callChildFunction = () => {
       this.child.handleActionParent();  ///calling a child function here
  } 
   render(){
      return (
           <div>
           {/* other things */}
           <Child ref={(cd) => this.child = cd}/>
           </div>
      )
    }
}

class Child extends React.Component {
   handleActionParent = () => {
       console.log('called from parent')
   }
   render() {
      return (
           {/*...*/}
      )
   }
}