Reactjs Question posted in
The new location for the React Documentation can be found here.

Reactjs – React Hook 'useEffect' Conditional Call Issue:

I’m currently working on a Next project and have encountered an issue related to the use Effect hook and conditional rendering. Below is a snippet of the code in question:

const ImageGeneration: React.FC<{
  subscribedUsersData: any
  error: any; // Replace 'any' with the actual type of error if possible
}> = ({ subscribedUsersData, error }) => {
  const isDisplayEnabled = IsDisplayEnabled();

  if (error) {
    return null; // or return some appropriate JSX here
  }

  useEffect(() => {
    const updateExpiryDate = async () => {
      // Your logic for updating expiry date goes here
    };

    updateExpiryDate();
  }, [subscribedUsersData]);

  // Rest of your component logic goes here

  return (
    // JSX for the component goes here
  );
};

I am specifically interested in having the if (error) statement at the top to avoid unnecessary execution of the use Effect block when an error is present. I would appreciate your insights on whether this approach is appropriate or if there are better practices for handling such scenarios.

Tags:

2

Answers


  1. 0

    React hooks can not be conditionally called, this breaks the Rules of Hooks.

    Only Call Hooks at the Top Level

    Don’t call Hooks inside loops, conditions, or nested functions. Instead, always use Hooks at the top level of your React function,
    before any early returns    . By following this rule, you ensure that
    Hooks are called in the same order each time a component renders.
    That’s what allows React to correctly preserve the state of Hooks
    between multiple useState and useEffect calls.

    The if (error) ... MUST come after all hooks in the component.

    If you want, you can include error in the dependency array and include it in some conditional call in the useEffect hook’s callback.

    Example:

    const ImageGeneration: React.FC<{
  subscribedUsersData: any
  error: any;
}> = ({ subscribedUsersData, error }) => {
  const isDisplayEnabled = IsDisplayEnabled();

  useEffect(() => {
    const updateExpiryDate = async () => {
      // Your logic for updating expiry date goes here
    };

    if (error) return; // <-- return early, don't run rest of effect

    updateExpiryDate();
  }, [error, subscribedUsersData]);

  if (error) {
    return null; // or return some appropriate JSX here
  }

  // Rest of your component logic goes here

  return (
    // JSX for the component goes here
  );
};
    Login or Signup to reply.
  2. 0

    In addition to Drew Reese’s answer.

    It seems that the error property only function is to avoid rendering the JSX of ImageGeneration (or rendering a fallback).

    It this case it’s easier to avoid calling ImageGeneration from the parent if there’s an error instead of passing the error:

    {!error && <ImageGeneration subscribedUsersData={subscribedUsersData} />}

    Or by rendering a fallback fallback:

    {error ? <div>{error}</div> : <ImageGeneration subscribedUsersData={subscribedUsersData} />}
    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search