How To Solve "Maximum update depth exceeded" In React (Set state)

Question

I'm getting the error :

"Maximum update depth exceeded. This can happen when a component repeatedly calls setState inside componentWillUpdate or componentDidUpdate. React limits the number of nested updates to prevent infinite loops."

import React, { Component } from "react";
import Form from "../Form/form";
import axios from "axios";

export default class Login extends Component {
  componentDidMount() {
    let url = "http://localhost:5060/users";

    axios.get(url).then(res => {
      console.log(res.data);
      this.setState({ users: res.data });
    });
  }


  getData(value) {

    let res;

    if (value.axios_res) {
      res = value.axios_res.data;
    }
    else{
        return
    }

    switch(res){

        case "user":
        console.log('Please Pick User');
        this.setState({ prompt: "Please Pick User" }) 
        break

        case "password":
        console.log('Please Fill Password');
        this.setState({ prompt: "Please Fill Password" })
        break

        case false:
        console.log('Wrong Password');
        this.setState({ prompt: "Wrong Password" })
        break

        case true:
        console.log("Loging in");
        this.setState({ prompt: "Loging in" })
        break

        default:
        console.log("Login");
    }
  }

  state = {
    users: [],
    prompt : "Welcome to Projector Helper"
  };

  render() {
    let form = [
      // Title
      {
        type: "select",
        name: "theater_name",
        placeholder: "Carmiel, Hifa",
        label: "Theater Name",
        options: this.state.users
      },
      {
        type: "password",
        name: "password",
        placeholder: "Password",
        label: "Password"
      }
    ];

    return (
      <div>
        <div className="row justify-content-center pt-5">
          <div className="col-6">
            <div className="card">
              <img
                src="http://www.kylelambert.com/gallery/stranger-things-netflix/images/stranger-things-season-2-poster-wide-by-kyle-lambert.jpg"
                alt=""
                height="200px"
              />
              <div className="card-body">
                <h5 className="card-title">Welcome</h5>
                <h6 className="card-subtitle mb-2 text-muted">
                  {this.state.prompt}
                </h6>
                <p className="card-text">
                  Please log in to the correct theater location, can't see
                  yourself on the list,
                  <br />
                  <a href="#">Register Now </a>
                </p>
                <Form
                  url="http://localhost:5060/login"
                  form={form}
                  submit="Login"
                  method="get"
                  data={value => this.getData(value)}
                />
              </div>
            </div>
          </div>
        </div>
      </div>
    );
  }
}

What I'm trying to do is update the state when I get a specific result from the server (therefore the switch).

The end result should show a different message every time you get a specific response.

Answer 1

The problem I had was with the data prop sent to the Form component. Its a mistake I fined myself do alot, next time ill try avoiding prop drilling and setting state more cautiously if at all. For me working with variables work way better most of the times.

Example:

username;
Getvalue(value){ 
This.username = value 
}

And not

Getvalue(value){ 
This.setstate({ username : value })
}

Unless its somthing that should be renderd on the DOM of course

Answer 2

This happens when you enter an infinite render loop - ie you call setstate (triggering render()) which somewhere down the line triggers another setstate (and another render()).

React keeps count on how many renders are triggered in a row and if you exceed the maximum count (maximum update depth), then it will throw this error and assume you have an infinite render loop problem.