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I'm learning react from the book full stack react. In one of the examples votingapp where you have products and a button to vote for the product. That button supposes to increase the number of votes for that product and I store the votes number in a component Parent's state and display it in a child component. That voting feature is not working.

I created Parent component where it displays child component that present product description, id, color and votes (the number of votes the product received)

import React, { Component } from 'react';

import './App.css';

import Product from "./Product";



var products = [

  {

    id: 1,

    name: "one",

    color: "blue",

    votes:0

  },

  {

    id: 2,

    name: "two",

    color: "green",

    votes : 0

  },

  {

    id: 3,

    name: "three",

    color: "Red",

    votes : 1

  }

];



class App extends Component {



  //this function will be passed to child component so the child can pass any data needed back to the parent using function argument.

  handleProductUpVote(productId) {

    console.log("Product #" + " " +productId + " was upvoted")

  };



  render() {

    const productComponents = products.map((product) => {

      return <Product

        key={"product-" + product.id}

        id={product.id}

        name={product.name}

        color={product.color}

        votes={product.votes}

        /*this is how we pass the function from parent to the child as a prop*/

        onVote={this.handleProductUpVote}

      />

    });

    return (

      <div className="App">

        {productComponents}

      </div>

    );

  }

}



export default App;

and here is my child component where it renders the product details

import React, { Component } from 'react';



class Product extends Component {

  constructor(props) {

    super(props);

    this.handleUpVote = this.handleUpVote.bind(this);

  }



  //using the function passed from parent in a child. We pass any data needed back to parent component using parent's function arugments 

  // invoke this function using onClick event inside the button 

  handleUpVote() {

    this.props.onVote(this.props.id);

  };



  render() {

    return (

      <div>

        <p> name: {this.props.name} </p>

        <p> MYcolor: {this.props.color} </p>

        {/*invoke the function using onClick so it will invoke handleUpVote that will update the prop and pass the data back to parent*/}

        <button onClick={this.handleUpVote}> Upvote Me </button>

        <p>{this.props.votes}</p>

        <hr></hr>

      </div>

    )

  }

};



export default Product;

this is working and I log to the console the message when I hit the button "Upvoteme"

But When I'm trying to move the setup to use state. It doesn't work Here is the parent component with the state and setState. When I click on the vote button nothing happens to the vote count.

import React, { Component } from 'react';

import './App.css';

import Child from "./Child";



var productseed = [

  {

    id: 1,

    name: "one",

    color: "blue",

    votes: 0

  },

  {

    id: 2,

    name: "two",

    color: "green",

    votes : 0

  },

  {

    id: 3,

    name: "three",

    color: "Red",

    votes : 1

  }

];



class Parent extends Component {

  constructor(props) {

    super(props);



    this.state = {

        products: ,

    };



    this.handleProductUpVote = this.handleProductUpVote.bind(this);

  }



  componentDidMount() {

    this.setState ({ products: productseed });

  }



  //this function will be passed to child component so the child can pass any data needed back to the parent using function argument.

  handleProductUpVote(productId) {

    // updating the vote in state

    const nextProducts = this.state.products.map((product) => {

      if (product.id === productId) {

        return Object.assign({}, product, {

          votes: product.votes + 1,

        });

      } else {

        return product

      }

    });



    this.setState({

      products: nextProducts,

    });

  }



  render() {

    const productComponents = productseed.map((product) => {

      return <Child

        key={"product-" + product.id}

        id={product.id}

        name={product.name}

        color={product.color}

        votes={product.votes}

        /*this is how we pass the function from parent to the child as a prop*/

        onVote={this.handleProductUpVote}

      />

    });



    return (

      <div className="App">

        parent

        {productComponents}

      </div>

    );

  }

}



export default Parent;

The line below suppose to point to the products in the state but when I highlight it, it doesn't highlight the products in the this.state.

The consolelog is logging the message to my developer console. This is the issue, products in this.setState isn't pointing to the this.state.products and therefore not updating the state.

componentDidMount() {

  this.setState({ products: productseed });

  console.log("this products not pointing to the this.state.products, why?")

}   

I read every question on stackoverflow related to setState not working and yet I have the same problem. If you an expert with react and able to take a look at this and figure out where is the issue, I would be so grateful. I'm unable to figure out when I assigned the this.setState({products: productseed}) and it doesn't update the state. I spent almost the past 4 hours reading and researching, please help.

Your problem lies in the render method of your Parent component. You're iterating over the productseeds array instead of your state. Since you're updating the state and not the seed array react sees no reason to rerender anything and therefore nothing changes.

So if you change that line from

const productComponents = productseed.map((product) => {...

to

const productComponents = this.state.products.map((product) => {...

you should be fine.

Moreover about your:

The line below suppose to point to the products in the state but when I highlight it, it doesn't highlight the products in the this.state.

This is just something related to the IDE you're using and nothing specific about react. You're passing an object with attributes and most IDEs (or all (?)) don't connect the combination with this.setState to the state object.