如何访问 function 作为在父组件中定义的子组件中的道具？

Question

I am trying to use a function as a prop in child component(DetailViewOfEntity) that is defined in the parent component(App.js) . When I click on the button,I am getting an error that this.setState and obj.detailview is not defined. Please also look at the image attached below for the exact error that I am getting.

Thank you

App.js component

import  React from "react";

import DetailViewOfEntity from "./DetailViewOfEntity";


export default class App extends React.Component {
  constructor(props, context) {
    super(props, context);

    this.viewEntity = this.ViewEntity.bind(this);

    this.state = {

        viewEntityState: false,
    
    };

  }


  }
  
  ViewEntity (para) {
    var obj = this;
    this.setState ({
      viewEntityState: true,
    });                                      

    obj.DetailView();//another function
  }

  DetailView() {
    console.log("we are in detail view function");
  }


  render() {

    return (
      <div>
        
        <DetailViewOfEntity 
            test = {this.ViewEntity}
        /> 
      </div>
    );
  }
}

DetailView Component

import React from "react";

export default class DetailViewOfEntity extends React.Component {
    constructor (props, context) {
        super (props, context);
    }

    UpdateCommentsFromCRM() {

        this.props.test(); //when i call this function, i got an error.
    }
  render () { 
      return (
          <div>

            <button onClick = {() => this.UpdateCommentsFromCRM()}>
            </button>
                     
          </div>
      );
  }
}

enter image description here

Answer 1

your problem is that you are calling:
this.viewEntity = this.ViewEntity.bind(this); instead of this.ViewEntity = this.ViewEntity.bind(this);

as @kapil pandey pointed out and here I share with you the working version on code sandbox

codesandbox demo

Answer 2

It's giving error because of function binding. If you using 'create-react-app' , you can omit the constructor and use arrow function . Hopefully, you won't give any error.