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Utility class to be used when implementing event-based APIs that allows for handlers registered via ::on to be invoked with calls to ::emit. Instances of this class are intended to be used internally by classes that expose an event-based API.

For example:

class User
  constructor: ->
    @emitter = new Emitter
 
  onDidChangeName: (callback) ->
    @emitter.on 'did-change-name', callback
 
  setName: (name) ->
    if name isnt @name
      @name = name
      @emitter.emit 'did-change-name', name
    @name

Construct an emitter.

@emitter = new Emitter()

Clear out any existing subscribers.

Unsubscribe all handlers.

Register the given handler function to be invoked whenever events by the given name are emitted via ::emit.

eventName

String naming the event that you want to invoke the handler when emitted.

handler()

Function to invoke when ::emit is called with the given event name.

Returns a Disposable on which .dispose() can be called to unsubscribe.

Register the given handler function to be invoked the next time an events with the given name is emitted via ::emit.

eventName

String naming the event that you want to invoke the handler when emitted.

handler()

Function to invoke when ::emit is called with the given event name.

Returns a Disposable on which .dispose() can be called to unsubscribe.

Register the given handler function to be invoked before all other handlers existing at the time of subscription whenever events by the given name are emitted via ::emit.

Use this method when you need to be the first to handle a given event. This could be required when a data structure in a parent object needs to be updated before third-party event handlers registered on a child object via a public API are invoked. Your handler could itself be preempted via subsequent calls to this method, but this can be controlled by keeping methods based on ::preempt private.

eventName

String naming the event that you want to invoke the handler when emitted.

handler()

Function to invoke when ::emit is called with the given event name.

Returns a Disposable on which .dispose() can be called to unsubscribe.

Invoke handlers registered via ::on for the given event name.

eventName

The name of the event to emit. Handlers registered with ::on for the same name will be invoked.

value

Callbacks will be invoked with this value as an argument.

Emitter essential

Construction and Destruction

::constructor()

::clear()

::dispose()

Event Subscription

::on(eventName, handler)

::once(eventName, handler)

::preempt(eventName, handler)

Event Emission

::emit(eventName, value)