How to Resolve the “Cannot Update a Component While Rendering a Different Component” Error in React

In this blog post, I will walk you through the process of fixing the “Cannot update a component (App) while rendering a different component” error in React. This error can be quite confusing, but with the right approach, it can be resolved.

The Error

Here’s the error message that you might come across while working on a React/Next.js application:

1	Cannot update a component (`App`) while rendering a different component

The Problem

The error occurs when you are trying to update a component’s state (App) while rendering a different component. In your case, the centralized state is managed in the App component, and you are trying to update it directly from a Next.js page component.

The Solution

To solve this problem, we need to make a small adjustment to your code. Instead of directly updating the state from the Next.js page component, we will use the useEffect hook to update the state only when the data changes. This way, we avoid updating the state while rendering a different component.

Here’s the updated code:

function MyApp({ Component, pageProps }) {
  const [lessonsRead, setLessonsRead] = useState(null);

  useEffect(() => {
    if (courseData && courseData.lessonsRead) {
      setLessonsRead(courseData.lessonsRead);
    }
  }, [courseData]);

  return (
    <Component
      lessonsRead={lessonsRead}
      setLessonsRead={setLessonsRead}
      {...pageProps}
    />
  );
}

By wrapping the code that updates the state in the useEffect hook and specifying [courseData] as the dependency array, we ensure that the state is only updated when the courseData changes.

With this modification, you should be able to fix the “Cannot update a component while rendering a different component” error in React.

I hope this quick guide helps you in resolving this error and improving your React development experience!

Tags: React, Next.js, useState, useEffect, component rendering