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event-kit

This is a simple library for implementing event subscription APIs.

Implementing Event Subscription APIs

const{Emitter}=require('event-kit')classUser{constructor(){this.emitter=newEmitter()}onDidChangeName(callback){this.emitter.on('did-change-name',callback)}setName(name){if(name!==this.name){this.name=namethis.emitter.emit('did-change-name',name)}returnthis.name}destroy(){this.emitter.dispose()}}

In the example above, we implement ::onDidChangeName on the user object, which will register callbacks to be invoked whenever the user's name changes. To do so, we make use of an internal Emitter instance. We use ::on to subscribe the given callback in ::onDidChangeName, and ::emit in ::setName to notify subscribers. Finally, when the User instance is destroyed we call ::dispose on the emitter to unsubscribe all subscribers.

Consuming Event Subscription APIs

Emitter::on returns a Disposable instance, which has a ::dispose method. To unsubscribe, simply call dispose on the returned object.

constsubscription=user.onDidChangeName((name)=>console.log(`My name is ${name}`))// Later, to unsubscribe...subscription.dispose()

You can also use CompositeDisposable to combine disposable instances together.

const{CompositeDisposable}=require('event-kit')constsubscriptions=newCompositeDisposable()subscriptions.add(user1.onDidChangeName((name)=>console.log(`User 1: ${name}`))subscriptions.add(user2.onDidChangeName((name)=>console.log(`User 2: ${name}`))// Later, to unsubscribe from *both*...subscriptions.dispose()

Creating Your Own Disposables

Disposables are convenient ways to represent a resource you will no longer need at some point. You can instantiate a disposable with an action to take when no longer needed.

const{Disposable}=require('event-kit')constdisposable=newDisposable(()=>this.destroyResource())

Using ES6 Code

You can use the ES6 style classes from lib directory.

const {Disposable} = require('event-kit/lib/event-kit')