CRUD and Redux: Updating Part 2

Posted by Kaitlin Kelly on September 1, 2019

In my last blog post I discussed how an edit action would work in my React/Redux application. To quickly sum it up, I added an edit button to each ‘wedding plan’ in my list of plans, and clicking this button would fetch the plan in question using the plan ID and pre-populate the input form with the plan’s information. I can then edit the information and re-submit the input form, and the plan’s information would re-write instead of write.

I ran into a challenge with this process that is worth sharing - what is the best way to pre-populate the state of the input form? In my last blog post, I tried utilizing the method constructor to set the state using my prop:

  constructor(props) {
    this.state = {
      description: props.plan.length == 0 ? "" : props.plan.description,
      vendor: props.plan.length == 0 ? "" : props.plan.vendor,
      location: props.plan.length == 0 ? "" : props.plan.location,
      time: props.plan.length == 0 ? "" : props.plan.time,
      completed: props.plan.length == 0 ? false : props.plan.completed,
      user_id: props.plan.length == 0 ? 0 : props.plan.user_id

This did not work. Even though my state was being updated immutably and Redux was capturing the difference, my component was not re-rendering. I then tried to set the state in componentDidMount, which, after experiencing this first hand, is a big no-no. This causes an endless loop of re-rendering. After a couple hours of researching I found a lifecycle method that works wonders, and that is componentWillReceiveProps:

  componentWillReceiveProps(nextProps) {
    if (nextProps.plan.description !== this.state.description) {
      this.setState({ description: nextProps.plan.description });
    if (nextProps.plan.vendor !== this.state.vendor) {
      this.setState({ vendor: nextProps.plan.vendor });
    if (nextProps.plan.location !== this.state.location) {
      this.setState({ location: nextProps.plan.location });
    if (nextProps.plan.time !== this.state.time) {
      this.setState({ time: nextProps.plan.time.replace("Z","") });
    if (nextProps.plan.completed !== this.state.completed) {
      this.setState({ completed: nextProps.plan.completed });
    if (nextProps.plan.user_id !== this.state.user_id) {
      this.setState({ user_id: nextProps.plan.user_id });

This method is able to compare the existing props to the upcoming props and will only set the state if a change is encountered. This avoids an endless loop.

HOWEVER, this is not the best option either. After reading React’s docs, this is not suggested either.


This lifecycle was previously named componentWillReceiveProps. That name will continue to work until version 17.

A suggestion around this?

If you used componentWillReceiveProps to “reset” some state when a prop changes, consider either making a component fully controlled or fully uncontrolled with a key instead.

After this information, even though my input form is successfully pre-populating, I am to tackle this from a different approach. My next path forward is making my input form fully controlled.

Stay tuned!