useQuery causes a component to render multiple times
  • 23-May-2023
Lightrun Team
Author Lightrun Team
Share
useQuery causes a component to render multiple times

useQuery causes a component to render multiple times

Lightrun Team
Lightrun Team
23-May-2023

Explanation of the problem

 

When using the new Hooks API in React, it is not uncommon for a component to re-render multiple times. This behavior can be observed in the provided example, where the useQuery hook from an external library causes the component to re-render three times. Here is a code snippet demonstrating this scenario:

const Detail = ({
  match: {
    params: { breed, id }
  }
}) => {
  const { data, error } = useQuery(GET_DOG, {
    variables: { breed }
  });
  console.log(2);
  return (
    <View style={styles.container}>
      <Header text={breed} />
      {error ? (
        <Error />
      ) : (
        <DogList...

 

In this example, the component logs the value 2 to the console. However, it is printed three times, indicating that the component is re-rendering multiple times. This behavior is not specific to the example but has been observed in other projects as well.

If you are experiencing similar behavior in your own project, it is important to understand that re-rendering can occur due to various factors such as changes in state, props, or the result of asynchronous operations. It is essential to analyze the component’s dependencies and ensure that unnecessary re-renders are minimized by optimizing hooks usage and avoiding excessive computations within the component body.

 

Troubleshooting with the Lightrun Developer Observability Platform

 

Getting a sense of what’s actually happening inside a live application is a frustrating experience, one that relies mostly on querying and observing whatever logs were written during development.
Lightrun is a Developer Observability Platform, allowing developers to add telemetry to live applications in real-time, on-demand, and right from the IDE.

  • Instantly add logs to, set metrics in, and take snapshots of live applications
  • Insights delivered straight to your IDE or CLI
  • Works where you do: dev, QA, staging, CI/CD, and production

Start for free today

Problem solution for: useQuery causes a component to render multiple times

 

Optimize Dependencies: Review the dependencies of the useQuery hook and ensure that only the necessary variables are included. This can be achieved by utilizing the second argument of the useQuery hook, which allows you to specify the dependencies that trigger the query. By providing a specific dependency list, you can prevent unnecessary re-execution of the query and subsequent re-renders. Here’s an example:

 

const { data, error } = useQuery(GET_DOG, {
  variables: { breed },
  // Specify the dependency list to trigger the query
  // only when 'breed' value changes
  skip: !breed,
});

 

By utilizing the skip option with an appropriate condition, you can control when the query should be executed and avoid unnecessary re-rendering.

Memoize Components: If the re-rendering is caused by props that are not changing frequently, you can memoize components using the React.memo higher-order component. This prevents unnecessary re-renders of the component by comparing the props and only updating if they have changed. Here’s an example:

 

const Detail = React.memo(({ match: { params: { breed, id } } }) => {
  const { data, error } = useQuery(GET_DOG, {
    variables: { breed },
  });
  console.log(2);
  // Component logic...
});

 

By wrapping the component with React.memo, you can optimize re-renders when the props remain the same.

Profile Performance: If the issue persists or if there are performance concerns, you can use React’s profiling tools, such as the Profiler component or the React DevTools, to analyze the component’s rendering behavior and identify potential bottlenecks. Profiling can help you pinpoint specific areas that are causing excessive re-renders and guide you in optimizing those areas.

 

Problems with react-apollo-hooks

 

Unnecessary Component Re-renders: Problem: When using react-apollo-hooks, components may re-render unnecessarily, leading to decreased performance. This can happen when the Apollo Client cache updates or when there are changes in the parent component that trigger re-renders of child components.

Solution: To optimize component re-renders, you can memoize the components using React’s React.memo or React.useMemo to prevent unnecessary updates. Additionally, you can make use of the useMemoOne hook from the use-memo-one library, which provides a more efficient way of memoizing values for improved performance.

Example:

 

import { useQuery } from 'react-apollo-hooks';

const MyComponent = React.memo(() => {
  const { data } = useQuery(GET_DATA);

  // Component logic...
});

 

Inconsistent Query Results: Problem: In some cases, react-apollo-hooks may return inconsistent query results due to caching. This can occur when the cache is not properly updated after mutations or when query results are not invalidated correctly.

Solution: To ensure consistent query results, you can manually update the cache after mutations using the update option provided by the mutation function. This allows you to modify the cache based on the mutation result and keep the data up-to-date. Additionally, you can use the refetchQueries option to explicitly refetch queries after mutations, ensuring that the cache is correctly updated with the latest data.

Example:

 

import { useMutation } from 'react-apollo-hooks';

const MyComponent = () => {
  const [updateData] = useMutation(UPDATE_DATA, {
    update: (cache, { data }) => {
      // Update cache manually based on mutation result
      cache.writeQuery({ query: GET_DATA, data });
    },
    refetchQueries: [{ query: GET_DATA }],
  });

  // Component logic...
};

 

Handling Loading and Error States: Problem: When making queries or mutations with react-apollo-hooks, handling loading and error states can be challenging, especially when rendering different UI components based on these states.

Solution: react-apollo-hooks provides the loading and error properties in the result of the query or mutation hook. You can utilize these properties to conditionally render loading or error components. Additionally, you can use the useQueryWithErrorHandling hook, available in some libraries like react-query or swr, to simplify error handling and display error messages.

Example:

 

import { useQuery } from 'react-apollo-hooks';

const MyComponent = () => {
  const { data, loading, error } = useQuery(GET_DATA);

  if (loading) {
    return <LoadingComponent />;
  }

  if (error) {
    return <ErrorComponent message={error.message} />;
  }

  return <DataComponent data={data} />;
};

 

A brief introduction to react-apollo-hooks

 

react-apollo-hooks is a library that provides a set of hooks for using Apollo Client with React applications. It simplifies the integration of Apollo Client into React components by offering a hook-based API, allowing developers to easily fetch and manage GraphQL data within their components. With react-apollo-hooks, developers can leverage the power of Apollo Client’s caching, query batching, and error handling capabilities while enjoying the simplicity and familiarity of React hooks.

One of the key advantages of react-apollo-hooks is its intuitive and declarative nature. By using hooks such as useQuery and useMutation, developers can seamlessly incorporate GraphQL queries and mutations into their components. These hooks abstract away the complexities of managing query states, loading indicators, error handling, and data updates, enabling a more streamlined and efficient development process. Additionally, react-apollo-hooks aligns with React’s functional component paradigm, promoting code reusability, separation of concerns, and easier testing.

 

Most popular use cases for react-apollo-hooks

 

  1. Fetching GraphQL Data: With react-apollo-hooks, you can easily fetch GraphQL data within your React components using the useQuery hook. This hook accepts a GraphQL query and returns the query result, including the data, loading state, and error information. Here’s an example:

 

import { useQuery } from 'react-apollo-hooks';
import { GET_USER } from './graphql/queries';

const UserProfile = ({ userId }) => {
  const { data, loading, error } = useQuery(GET_USER, {
    variables: { id: userId },
  });

  if (loading) {
    return <div>Loading...</div>;
  }

  if (error) {
    return <div>Error: {error.message}</div>;
  }

  const user = data.user;

  return (
    <div>
      <h1>{user.name}</h1>
      <p>{user.email}</p>
    </div>
  );
};

 

  1. Mutating GraphQL Data: react-apollo-hooks also provides hooks for performing GraphQL mutations, such as creating, updating, or deleting data. The useMutation hook simplifies the process of executing mutations and handling the mutation result. It provides a convenient way to trigger mutations and access the mutation response. Here’s an example:

 

import { useMutation } from 'react-apollo-hooks';
import { CREATE_POST } from './graphql/mutations';

const CreatePostForm = () => {
  const [title, setTitle] = useState('');
  const [content, setContent] = useState('');

  const createPost = useMutation(CREATE_POST);

  const handleSubmit = async (e) => {
    e.preventDefault();

    try {
      const { data } = await createPost({
        variables: { title, content },
      });

      console.log('New post created:', data.createPost);
      // Handle success or perform any necessary actions
    } catch (error) {
      console.error('Error creating post:', error);
      // Handle error or display error message
    }
  };

  return (
    <form onSubmit={handleSubmit}>
      <input
        type="text"
        placeholder="Title"
        value={title}
        onChange={(e) => setTitle(e.target.value)}
      />
      <textarea
        placeholder="Content"
        value={content}
        onChange={(e) => setContent(e.target.value)}
      />
      <button type="submit">Create Post</button>
    </form>
  );
};

 

  1. Local State Management: In addition to fetching and mutating remote GraphQL data, react-apollo-hooks also provides hooks for managing local state with Apollo Client. The useApolloClient hook gives you access to the Apollo Client instance, allowing you to read from and write to the local cache. This enables you to manage local state and perform actions such as updating cached data or triggering cache invalidation. Here’s an example:

 

import { useApolloClient } from 'react-apollo-hooks';

const LogoutButton = () => {
  const client = useApolloClient();

  const handleLogout = () => {
    // Perform logout logic

    // Clear local cache and reset Apollo Client
    client.resetStore();
  };

  return <button onClick={handleLogout}>Logout</button>;
};

 

In summary, react-apollo-hooks provides a set of hooks that streamline the process of fetching GraphQL data, performing mutations, and managing local state within React components. These hooks simplify the integration of Apollo Client with React, allowing you to build powerful and efficient GraphQL-powered applications with ease.

Share

It’s Really not that Complicated.

You can actually understand what’s going on inside your live applications.

Try Lightrun’s Playground

Lets Talk!

Looking for more information about Lightrun and debugging?
We’d love to hear from you!
Drop us a line and we’ll get back to you shortly.

By clicking Submit I agree to Lightrun’s Terms of Use.
Processing will be done in accordance to Lightrun’s Privacy Policy.