React get new data in componentDidUpdate

Question

I have a component which receives a list of news from two or three APIs. the first time the component renders, the apis are called and data is rendered in componentDidMount something like this:

componentDidMount() {
        this.state.platforms.forEach((platform, i) => {
            let objToSend = {
                phrase: this.props.searchParams.phrase,
                // this is the main place when input data changes
                ...this.props.searchParams.general_params,
                ...this.props.searchParams.platforms[i].api_params,
                stringPath: platform,
                apiPath: this.props.searchParams.platforms[i].apiPath,
            }
            this.props.loadData(objToSend)
            // this is the api call using redux which sends data as props to this component
 }

new when the phrase change, I want this component to re-render and re-run the componentDidMount, but it's not working because componentDidMount will run once. So I used componentDidUpdate, but as there are a number of calls so the api is being updated continuesly.

How can I make the component re-render and re-run componentDidMount every time I change the phrase

score 5 · Answer 1 · answered Aug 24 '19 at 07:06

You can use componentDidUpdate arguments (previousProps, previousState) to check whether some new changes happened.

Example

componentDidUpdate(previousProps, previousState) {
    if (previousProps.phrase !== this.props.phrase) {
        //Do whatever needs to happen!
    }
}

I stopped the infinite loop for my situation this way.

score 3 · Accepted Answer · answered Jan 06 '19 at 13:29

Here's one way to do something() when you re-render.

import React, { Component } from 'react';
import { render } from 'react-dom';

const fakeFetch = (n) => {
  console.log(`Doing fake fetch: ${n}`)
  return n
}

class App extends Component {
  state = {
    value: false,
    number: 0,
  }

  componentDidMount() {
    const number = fakeFetch(this.state.number + 1);
    this.setState({ number })
  }

  componentDidUpdate(prevProps, prevState) {
    if (prevState.value !== this.state.value) {
      const number = fakeFetch(this.state.number + 1);
      this.setState({ number })
    }
  }

  toggle = () => {
    this.setState(({ value }) => ({ value: !value }))
  }

  render() {
    return (
      <React.Fragment>
        <h1>Number: {this.state.number}</h1>
        <button onClick={this.toggle}>re-render</button>
      </React.Fragment>
    );
  }
}

render(<App />, document.getElementById('root'));

Live example here.

React get new data in componentDidUpdate

2 Answers2