HarmonyConductor

Harmony: Conductor is a lightweight, easy-to-use event bus for managing application-level events. This simple yet powerful tool facilitates communication between different parts of your application without tight coupling.

Features

• Event Subscriptions: Subscribe to events with custom handlers.
• Event Publishing: Publish events with optional payloads.
• Type Safety: Generic support for event payloads.

Installation

Install HarmonyConductor via npm:

npm install harmony-conductor

Or using Yarn:

yarn add harmony-conductor

Usage

Importing

First, import the HarmonyConductor library into your project:

import { Conductor } from 'harmony-conductor';

Event Subscriptions

To subscribe to an event, use the Conductor.Subscribe method. You can provide an event name and a handler function.

Conductor.Subscribe('myEvent', payload => {
    console.log('Event payload:', payload);
});

For events without a payload:

Conductor.Subscribe('simpleEvent', () => {
    console.log('Simple event triggered');
});

Event Publishing

To trigger an event, use Conductor.Publish. You can provide the event name and an optional payload.

Conductor.Publish('myEvent', { key: 'value' });

For events without a payload:

Conductor.Publish('simpleEvent');

Unsubscribing from Events

When you no longer need to listen to an event, you can unsubscribe from it. Use the UnSubscribe method available on the subscription object returned when subscribing:

const subscription = Conductor.Subscribe('myEvent', payload => {
    console.log('Event payload:', payload);
});

// Later, when you want to unsubscribe
subscription.UnSubscribe();

API

Subscribe to an event.

Conductor.Subscribe<TEvent>(eventName: string, handler: (payload: TEvent) => void, thisArg?: object): ISubscription<TEvent>

• eventName: The name of the event to subscribe to.
• handler: The function to call when the event is published.
• thisArg (optional): An object to bind as this when calling the handler.

Publish an event.

Conductor.Publish<TEvent>(eventName: string, payload?: TEvent): void

• eventName: The name of the event to publish.
• payload (optional): Data to pass to the event handler.

Manage a subscription.

The ISubscription<TEvent> interface represents a subscription to an event.

• Subscriber: A function that will be called when the event is published, with an optional payload of type TEvent.
• EventName: The name of the event to which the subscription is associated.
• UnSubscribe: A parameterless method to unsubscribe from the event, removing the subscription.

You can use the UnSubscribe method to remove a subscription when it's no longer needed, preventing further callbacks to the Subscriber function.

Advanced Usage

Using Typed Events

You can create a typed event class to encapsulate the data you want to pass with the event. Define a typed event class:

class UserCreatedEvent {
    constructor(userName?: string, email?: string) {
        this.UserName = userName;
        this.Email = email;
    }
    public UserName?: string
    public Email?: string
}

And an Enum to represent event names:

enum AppEvents {
    UserCreated = "UserCreated"
}

Subscribing with a Class Method

Subscribe to an event using a method of a TypeScript class, ensuring proper binding of the this context:

class AppComponent {
    constructor() {
        Conductor.Subscribe(AppEvents.UserCreated, this.onUserCreated, this);
    }
    private onUserCreated(event: UserCreatedEvent): void {
        console.log(`New user created: ${event.UserName}, Email: ${event.Email}`);
    }
}

Publishing Typed Events

Publishing typed events is straightforward. Pass the event name and the event object:

const userCreatedEvent = new UserCreatedEvent('johndoe', '[e-mail]');
Conductor.Publish(AppEvents.UserCreated, userCreatedEvent);

This example shows how Conductor can be used with TypeScript classes and typed events, offering a clean and type-safe way to handle events in your application.

Running Tests

To ensure Conductor functions as expected, there is a comprehensive test suite. After installing the necessary dependencies, run these tests using the following command:

npm test

Contributing

Contributions to Harmony: Conductor are welcome! Please contact the author to get started.

License

This project is licensed under the MIT License.