Understanding of the higher-order components React

1. Basic Concepts

Component to high-order component is a parameter, the function returns a value of the new component.

 

2 illustrates

① decoration factory pattern

Component is the basic unit react in, there is usually some logical component (non-rendering) required multiplexing processing. Here we can encapsulate some of the internal components in common with the higher-order components.

When unencapsulated, you can not reuse the same logic:

Render comments list

class CommentList extends React.Component {
  constructor(props) {
    super(props);
    this.handleChange = this.handleChange.bind(this);
    this.state = {
      // assumed "DataSource" is a data source variable within a global scope
      comments: DataSource.getComments()
    };
  }

  componentDidMount() {
    // Subscribe to changes
    DataSource.addChangeListener(this.handleChange);
  }

  componentWillUnmount() {
    // Clear subscription
    DataSource.removeChangeListener(this.handleChange);
  }

  act change () {
    // When updating the data source, the update component status
    this.setState({
      comments: DataSource.getComments()
    });
  }

  render() {
    return (
      <div>
        {this.state.comments.map((comment) => (
          <Comment comment={comment} key={comment.id} />
        ))}
      </div>
    );
  }
}

Rendering blog list

lass BlogPost extends React.Component {
  constructor(props) {
    super(props);
    this.handleChange = this.handleChange.bind(this);
    this.state = {
      blogPost: DataSource.getBlogPost(props.id)
    };
  }

  componentDidMount() {
    DataSource.addChangeListener(this.handleChange);
  }

  componentWillUnmount() {
    DataSource.removeChangeListener(this.handleChange);
  }

  act change () {
    this.setState({
      blogPost: DataSource.getBlogPost(this.props.id)
    });
  }

  render() {
    return <TextBlock text={this.state.blogPost} />;
  }
}

Borrow higher order component, a common logical package:

const CommentListWithSubscription = withSubscription(
  CommentList,
  (DataSource) => DataSource.getComments()
);

const BlogPostWithSubscription = withSubscription(
  BlogPost,
  (DataSource, props) => DataSource.getBlogPost(props.id)
);

Processing components (processing: Processing common logical) plant, the old receiving component, the new component Returns:

// This function receives a component ...
function withSubscription(WrappedComponent, selectData) {
  // ... and return to another component ...
  return class extends React.Component {
    constructor(props) {
      super(props);
      this.handleChange = this.handleChange.bind(this);
      this.state = {
        data: selectData(DataSource, props)
      };
    }

    componentDidMount() {
      // ... responsible for the subscription-related operations ...
      DataSource.addChangeListener(this.handleChange);
    }

    componentWillUnmount() {
      DataSource.removeChangeListener(this.handleChange);
    }

    act change () {
      this.setState({
        data: selectData(DataSource, this.props)
      });
    }

    render() {
      // ... and use the new data rendering components are packed!
      // Note that we may also transfer other property
      return <WrappedComponent data={this.state.data} {...this.props} />;
    }
  };
}

　

 

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