React - HOCs Inside Render - Are there Exceptions to the Rule?

Question

I implemented a Pub/Sub pattern by using several component composition techniques: React.cloneElement, and functional "composed components." The goal in mind was to be able to dynamically enroll components into different flows of data by assigning them a "topic" prop.

For example, this component receives all data published to the HELLO_WORLD topic:

 <MyComponent topic="HELLO_WORLD" />

Here is the inside of MyComponent expressed as a functional component:

export const MyComponent = props => subscribe(({ topic, data }) => {
    return <span>I am listening to the {topic} topic. Current state: {data}</span>
}, props.topic);

Alternatively, here it is expressed as a class component:

class MyComponent extends React.Component {
    render() {
        const { props: { otherProps, topic } } = this;
        return subscribe(({ data }) => {
            return <span>I am listening to the {topic} topic. Current state: {data}</span>
        }, topic)
    }
}

As you can see, this pattern necessitated returning a Higher Order Component inside the render function. Do you think this falls into the caveat mentioned here?

Here's some more context:

The subscribe function returns a composed component:

const subscribe = (Comp, topic) => {
  return (
    <Subscriber topic={topic}>
      <Comp />
    </Subscriber>
  );
};

Which wraps MyComponent in a Subscriber:

class Subscriber extends Component {
    state = publisher.getState(this.props.topic) // get initial state

    onMessage = msg => {
        this.setState({ ...msg });
        return this.state;
    }

    componentDidMount() {
        this.subscription = publisher
            .subscribe(this.props.topic, this.onMessage);
    }
    
    componentWillUnmount() {
        publisher.unsubscribe(this.props.topic, this.onMessage);
    }

    render() {
        const {
            state: { data },
            props: { children }
        } = this;
        return Children.map(children, child =>
            cloneElement(child, { ...this.props, data })
        );
    }
}

The subscriber gets its state from the publisher, which caches topics:

const eventEmitter = new EventEmitter();

const publisher = {
  subscribe: function (eventName, cache) {
    eventEmitter.on(eventName, data => {
      this.cache[eventName] = cache(data);
    });
  },
  unsubscribe: function (eventName, fn) {
    eventEmitter.off(eventName, fn)
  },
  send: function (eventName, payload) {
    eventEmitter.emit(eventName, payload);
    if (!this.cache[eventName]) {
      this.cache[eventName] = { data: payload };
    }
  },
  getState: function (topic) {
    return this.cache[topic] || {};
  },
  cache: {}
}

The component profiler suggests that this setup is rendering very efficiently. Additionally, state is persisted in a cache outside of React land. If you ask me, it's pretty much just Flux with a twist. Your thoughts?

Answer 1

Your subscribe() is not a true HOC.

Why ? ( concentrate on bold word )

• HOC is a pure Function that returns a container component which wraps original component.
• subscribe() is just wrapper Component which just wraps original component and return.

Here is a detailed answer : https://stackoverflow.com/a/64178585/8323442