useQuery causes a component to render multiple times

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.

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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.

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

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

  // Component logic...
});

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...
};

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} />;
};

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>
  );
};

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>
  );
};

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>;
};