import React, {Component};


class ParentComponent extends Component {
  //Initial State
  state = { data: [] }

  //Function to update the state
  //NOTE-1: You only can use this.setState to update the state
  //NOTE-2: You never want to update your state directly that why I use .concat instead of .push.
  addElementIntoState = (element) => {
    this.setState({data: this.state.data.concat(element)})
  }
  render(){
    return (
      // Passing the callback function via props into child
      // Each time the child executes this function the parent will know that its state is being updated.
      // And will re-render with the new state.
      <MyChild addElementIntoState={addElementIntoState}>
    )
  }
}