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() {
this.emitter = new Emitter()
}
onDidChangeName(callback) {
this.emitter.on('did-change-name', callback)
}
setName(name) {
if (name !== this.name) {
this.name = name
this.emitter.emit('did-change-name', name)
}
return this.name
}
}
Construct an emitter.
this.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.
Argument | Description |
---|---|
|
String naming the event that you want to invoke the handler when emitted. |
|
Function to invoke when ::emit is called with the given event name. |
Return values |
---|
Returns a Disposable on which
|
Register the given handler function to be invoked the next time an events with the given name is emitted via ::emit.
Argument | Description |
---|---|
|
String naming the event that you want to invoke the handler when emitted. |
|
Function to invoke when ::emit is called with the given event name. |
Return values |
---|
Returns a Disposable on which
|
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.
Argument | Description |
---|---|
|
String naming the event that you want to invoke the handler when emitted. |
|
Function to invoke when ::emit is called with the given event name. |
Return values |
---|
Returns a Disposable on which
|