Re-render React component when prop changes

componentWillReceiveProps() is going to be deprecated in the future due to bugs and inconsistencies. An alternative solution for re-rendering a component on props change is to use componentDidUpdate() and shouldComponentUpdate().

componentDidUpdate() is called whenever the component updates AND if shouldComponentUpdate() returns true (If shouldComponentUpdate() is not defined it returns true by default).

shouldComponentUpdate(nextProps){
    return nextProps.changedProp !== this.state.changedProp;
}

componentDidUpdate(props){
    // Desired operations: ex setting state
}

This same behavior can be accomplished using only the componentDidUpdate() method by including the conditional statement inside of it.

componentDidUpdate(prevProps){
    if(prevProps.changedProp !== this.props.changedProp){
        this.setState({          
            changedProp: this.props.changedProp
        });
    }
}

If one attempts to set the state without a conditional or without defining shouldComponentUpdate() the component will infinitely re-render

You have to add a condition in your componentDidUpdate method.

The example is using fast-deep-equal to compare the objects.

import equal from 'fast-deep-equal'

...

constructor(){
  this.updateUser = this.updateUser.bind(this);
}  

componentDidMount() {
  this.updateUser();
}

componentDidUpdate(prevProps) {
  if(!equal(this.props.user, prevProps.user)) // Check if it's a new user, you can also use some unique property, like the ID  (this.props.user.id !== prevProps.user.id)
  {
    this.updateUser();
  }
} 

updateUser() {
  if (this.props.isManager) {
    this.props.dispatch(actions.fetchAllSites())
  } else {
    const currentUserId = this.props.user.get('id')
    this.props.dispatch(actions.fetchUsersSites(currentUserId))
  }  
}

Using Hooks (React 16.8.0+)

import React, { useEffect } from 'react';

const SitesTableContainer = ({
  user,
  isManager,
  dispatch,
  sites,
}) => {
  useEffect(() => {
    if(isManager) {
      dispatch(actions.fetchAllSites())
    } else {
      const currentUserId = user.get('id')
      dispatch(actions.fetchUsersSites(currentUserId))
    }
  }, [user]); 

  return (
    return <SitesTable sites={sites}/>
  )

}

If the prop you are comparing is an object or an array, you should use useDeepCompareEffect instead of useEffect.