Observables and Promises

Asynchronous programming in World of Warcraft is a good thing when using it in the correct places.

Observables

An observable is an event stream that can live infinitly and notifies all subscribers when something happens. They should be unsubscribed if no newer event should be received.

There are two main classes.

• Observable
• Subscription

An observable will create a subscription when you subscribed to an observable (via .subscribe(...)). This subscription can be unsubscribed (via .unsubscribe()).

One example for reactive programming: I want to get notified when unit health changes.

import { observableFromEvent } from "@wartoshika/wow-qhun-core-ts/src/core";

// listen to UNIT_HEALTH event
const subscription = observableFromEvent("UNIT_HEALTH")
  // subscribe to this event and every time one unit looses or gains health i shall be notified
  .subscribe(unit => {

    // print the unitId
    print(`unit was ${unit[0]}`);
});

// later in the future
subscription.unsubscribe();

A more complex example: I want to get notified when player health changes.

import { observableFromEvent } from "@wartoshika/wow-qhun-core-ts/src/core";

// listen to UNIT_HEALTH event
const subscription = observableFromEvent("UNIT_HEALTH")
    // before i should be notified, make sure that only player changes passes.
    .filter(unit => unit[0] === "player")
    // subscribe to this event and every time one unit looses or gains health i shall be notified
    .subscribe(unit => {

        print(`unit was ${unit[0]}`);
    });

// later in the future
subscription.unsubscribe();

Promises

Promises are a one time asynchronous request/response thing. They can be resolved when the request succeded or rejected when an error occurs. The resolved Promise may have a payload attached.

One example for Promises: I shall get notified when i raise from the dead.

import { EventUtil } from "@wartoshika/wow-qhun-core-ts/src/core";

EventUtil.getPromise("PLAYER_ALIVE", 10000).done(() => {
    print("I am alive!");
}, reason => {
    print("I shall life under the dead...");
});

The promise will try 10 seconds to be resolved via PLAYER_ALIVE event. If the timeout exceeds, the promise will be rejected.

Tip: Every Observable can be converted to a Promise using .toPromise() method on observables.