TypeError: Variable in Object State is not iterable

Question

i'm very new to react.js and i got a question about my program. I am getting a type error when i try to invoke a method when the corresponding buttton is clicked. Basically the method generates a random number and i want to display this number in another component. For this to work i have to write the return in the variable 'defNum' located in the object state. I hope you can help me:)

My Code in the context.js :

  defaultNumber = () => {
    let defNumChange = [...this.state.defNum];
    defNumChange = Math.random().toString(8).substr(2);
    defNumChange = parseInt(defNumChange);
    console.log(defNumChange);
    this.setState(() => {
  return {
    defNum: defNumChange,
  };
});

And this is my state object also located in the context.js:

  state = {
    products: [],
    detailProduct: detailProduct,
    cart: [],
    modalOpen: false,
    modalProduct: detailProduct,
    subTotal: 0,
    delivery: 0,
    totalSum: 0,
    defNum: 0,
  };

This is the component where i want to display my return value of the method:

import React, { Component } from "react";
import { ProductConsumer } from "../context";

export default class thankYou extends Component {
render() {
return (
  <ProductConsumer>
    {(value) => {
      const { defNum } = value;
      return (

        <React-Fragement>
          <div className="container">
            <div className="row mt-2 mb-2">
              <div className="col-md-12">
                <div className="jubotron text-center text-titel">

                  <p></p>
                  <h4>Vielen Dank für deine Bestellung!</h4>
                  <hr />
                  <p className="mt-6">
                    Wenn dir unsere Produkte gefallen komme gerne wieder auf
                    uns zurück
                  </p>

                  <p className="mt-6">
                    <strong>
                      Dein .Dog.Styles. Team freut sich auf dich
                    </strong>
                  </p>
                  <p className="mt-6">
                    Bitte überprüfe deine E-Mails, um weitere Details zu
                    erhalten.
                  </p>
                  <hr />
                  <p></p>

                  <p className="mt-6">
                    <strong>Deine Bestellnummer: {defNum} </strong>      <------ THIS ONE :)
                  </p>
                </div>
              </div>
            </div>
          </div>
        </React-Fragement>
      );
    }}
  </ProductConsumer>
);}}

Answer 1

Your defnum is integer as per your state (0) and its not iterable.It should either be an array or Set or object or string to be iterable.

let defNumChange = [...this.state.defNum]; // so this won't work 

Spread syntax (...) allows an iterable such as an array expression or string to be expanded in places where zero or more arguments (for function calls) or elements (for array literals) are expected,or an object expression to be expanded in places where zero or more key-value pairs (for object literals) are expected

See doc here

What you can do is,add double quotes to the value (Just a hack) of defnum to make it iterable

 state = {
    products: [],
    detailProduct: detailProduct,
    cart: [],
    modalOpen: false,
    modalProduct: detailProduct,
    subTotal: 0,
    delivery: 0,
    totalSum: 0,
    defNum: "0", // as string is iterable this will work
  };