react-observer-pattern

A simple Observer pattern implementation for React applications. This library provides Subject and Observer classes that allow you to implement the observer pattern and manage state updates across multiple React components without a global state management library.

Installation

You can install this package via npm:

npm install @mozart25/react-observer

Usage

1. Example: Using react-observer-pattern in a React application Here’s an example of how you can use the Subject and Observer classes in a React application to manage shared state between components.

// App.js
import React, { useEffect, useState } from "react";
import { Subject, Observer } from "@mozart25/react-observer";

// Create a subject instance
const subject = new Subject();

// ObserverComponent: A component that subscribes to the Subject
const ObserverComponent = ({ label }) => {
  const [state, setState] = useState("Initial State");

  useEffect(() => {
    // Create a new Observer for each component and subscribe it to the Subject
    const observer = new Observer(setState);
    subject.subscribe(observer);

    // Cleanup function to unsubscribe the observer when the component unmounts
    return () => {
      subject.unsubscribe(observer);
    };
  }, []);

  return (
    <div>
      <p>
        {label}: {state}
      </p>
    </div>
  );
};

// App component
const App = () => {
  return (
    <div>
      <h1>Observer Pattern Example in React</h1>

      {/* Components that listen to the same Subject */}
      <ObserverComponent label="Component 1" />
      <ObserverComponent label="Component 2" />

      {/* Button to trigger state change */}
      <button onClick={() => subject.notify("Updated State")}>
        Notify All
      </button>
    </div>
  );
};

export default App;

Key Features:

• Subject: Manages a list of Observers and notifies them when state changes.
• Observer: Each observer subscribes to the Subject and updates its state when notified.
• This example demonstrates how multiple React components can subscribe to the same Subject and respond to state changes.