README.md

Class Component Data Fetching with componentDidMount

This example demonstrates legacy React data fetching patterns using class components and the componentDidMount lifecycle method.

Key Learning Points

• Class Components: Uses React class components instead of functional components
• componentDidMount: Fetches data when component mounts using the componentDidMount lifecycle
• componentDidUpdate: Refetches data when route parameters change
• Manual State Management: Uses this.setState() for managing loading, error, and data states
• Fetch API: Direct usage of browser fetch() API without abstractions
• Manual Loading States: Explicit handling of loading, error, and success states

Code Examples

Basic Data Fetching in componentDidMount

// HomePage.tsx:53-55
componentDidMount() {
  this.fetchPosts();
}

// HomePage.tsx:32-51
fetchPosts = async () => {
  const { posts } = this.state;

  if (!posts.length) {
    this.setState({ isLoadingPosts: true });
  }
  this.setState({ isFetchingPosts: true });

  try {
    const fetchUrl = new URL(`http://localhost:3300/posts`);
    const response = await fetch(fetchUrl.href);
    const fetchedPosts = (await response.json()) as IPost[];
    this.setState({ posts: fetchedPosts });
  } catch (error) {
    console.error(error);
    this.setState({ isErrorLoadingPosts: true });
  } finally {
    this.setState({ isLoadingPosts: false, isFetchingPosts: false });
  }
};

Refetching on Route Parameter Changes

// PostPage.tsx:83-89
componentDidUpdate(prevProps: PostPageProps) {
  if (prevProps.params.id !== this.props.params.id) {
    this.fetchPost();
    this.fetchUser();
    this.fetchComments();
  }
}

Manual State Management Pattern

// PostPage.tsx:17-42
interface HomePageState {
  posts: IPost[];
  isLoadingPosts: boolean;
  isErrorLoadingPosts: boolean;
  isFetchingPosts: boolean;
}

state: HomePageState = {
  posts: [],
  isLoadingPosts: false,
  isErrorLoadingPosts: false,
  isFetchingPosts: false,
};