Cannot read properties of null (reading 'useMemo')

help
1

Hey guys,
we are using Meteor + React with the SSR package. When I do multiple request on the same page, the app crashes with the following error message on the server side:

Cannot read properties of null (reading 'useMemo')

The component where I use useMemo looks like this:

function myComponent() {

const value = useMemo(() => { .. some code ..},[location.pathname]);
}

I import useMemo like this:

import {useEffect, useMemo} from 'react';

Does anybody have an idea what could cause the issue? If I remove useMemo, everything works finde. I’ve already checked for multiple React version but only have 1 (18.2.0)? I’m wondering why it works on a single request but fails on multiple requests at once?

// Edit:

I noticed that the issue is caused by another hook which I use to load initial data on the server side, which gets passed to the client.

 useRunOnce(() => {
        if (Meteor.isServer) {

            Meteor.wrapAsync(async (cb) => {
                await loadCategory();
                cb();
            })();

        }
    });

It seems that a delay causes the issue. I get the same error when I do something like this:

 useRunOnce(() => {
        if (Meteor.isServer) {

            Meteor.wrapAsync(async (cb) => {
               setTimeout(() => {cb()},5000);
            })();

        }
    });

So I basically want to block “rendering” on the server side until the initial data has been loaded. Is this an anti-pattern?

2

React hooks cannot be ran after async functions. Not familiar with server side but on the client you don’t block rendering. You do a conditional rendering where you render something like until you get something better to render.

if (block_render) {
   return <span />
}

return (
   <div>something_more_serious</div>
)