Strongly Typed Events

Add the power of events to your projects. We even have 3 flavors for you.

Event types

This project gives you the following event types:

• Events - styled after the way .Net implements events. With each event you'll get a sender and an argument object. If you use typescript, you can implement them using generics.
  npm install ste-events or npm install ste-promise-events for event handlers that support Promise.
• Simple events - basically the same thing, with only an argument.
  npm install ste-simple-events or npm install ste-promise-simple-events for event handlers that support Promise.
• Signals - for when no data is needed, just the firing of the event is enough.
  npm install ste-signals or npm install ste-promise-signals for event handlers that support Promise.
• You want them all? Just use
  npm install strongly-typed-events.

Subscription made easy

An example says more than a 1000 words. Imagine if you have events like this on your class:

let clock = new Clock("Smu", 1000);

//log the ticks to the console - this is a signal event
clock.onTick.subscribe(() => console.log("Tick!"));

//log the sequence parameter to the console - this is a simple event
clock.onSequenceTick.subscribe(s => console.log(`Sequence: ${s}`));

//log the name of the clock and the tick argument to the console - this is an event
clock.onClockTick.subscribe((c, n) =>
  console.log(`${c.name} ticked ${n} times.`)
);

Events made easy

So let's look at the implementation from a TypeScript perspective. (Do you program NodeJs without typescript? Check this.)

import { SignalDispatcher, SimpleEventDispatcher, EventDispatcher } from "strongly-typed-events";

class Clock {
  private _onTick = new SignalDispatcher();
  private _onSequenceTick = new SimpleEventDispatcher<number>();
  private _onClockTick = new EventDispatcher<Clock, number>();
  private _ticks: number = 0;

  constructor(public name: string, timeout: number) {
    setInterval(() => {
      this._ticks += 1;
      this._onTick.dispatch();
      this._onSequenceTick.dispatch(this._ticks);
      this._onClockTick.dispatch(this, this._ticks);
    }, timeout);
  }

  public get onTick() {
    return this._onTick.asEvent();
  }

  public get onSequenceTick() {
    return this._onSequenceTick.asEvent();
  }

  public get onClockTick() {
    return this._onClockTick.asEvent();
  }
}

Stopping events

You can stop events from being propagated.

let dispatcher = new SignalDispatcher();

  let a = 0;
  dispatcher.sub(ev => {
    a++;
    if (a > 2) {
      ev.stopPropagation();
    }
  });

  let b = 0;
  dispatcher.sub(() => { b++; });

  dispatcher.dispatch();
  dispatcher.dispatch();
  dispatcher.dispatch();
  dispatcher.dispatch();

  // a should be 4, because 4 dispatches are done.");
  // b should be 2, because events after the 2nd dispatch are stopped."

Check the documentation or the examples for more information.

Documentation

This project will help you to add events, event handling en event dispatching to your classes. To get you started, check:

• How to add an event to a class?
• How to add an event to an interface?
• How to add multiple events to a class?
• How to add dynamic named events to a class?
• How to do asynchronous event dispatching?
• On events, dispatchers and lists (a general explanation of the system)
• How to use Strongly Typed Events in Node.js?
• Some unsubscribe strategies

History

Click here for more history...

Packages

Want a smaller package? Check out on of these:

Package	Description
ste-core	Package that contains all the building blocks for the creation of events. The dispatcher implementation is its main hero.
ste-events or ste-promise-events	Events that are modeled after .Net with a sender and argument. If you use typescript, you can leverage the support for generics and get strongly typed code.
ste-simple-events or ste-promise-simple-events	A simpler version of the ste-event-event. No sender, just an argument.
ste-signals or ste-promise-signals	A signal is even simpler, it is just a callback for when you need to be alerted without any scope.
strongly-typed-events	This package includes everything.
ste-browser	Helps to host events in the browser.

Maintenance

This project is maintained by Kees C. Bakker.