Event

Events are deepstream’s implementation of the publish/subscribe pattern. You can find more about how they are used in the events tutorial.

Methods

client.event.subscribe( event, callback )

Argument	Type	Optional	Description
event	String	false	An eventname
callback	Function	false	A function that will be called whenever the event is emitted

Subscribes to an event. Callback will receive the data passed to emit()

// Client A
client.event.subscribe('news/sports', data => {
  // handle published data
})

// Client B
client.event.emit('news/sports', /* data */)

client.event.unsubscribe( event, callback )

Argument	Type	Optional	Description
event	String	false	An eventname
callback	Function	true	The callback that was previously registered with subscribe. If the callback is omitted, all listeners for the event will be removed

Unsubscribes from an event that was previously registered with subscribe(). This stops a client from receiving the event.

// Client A
client.event.unsubscribe('news/politics', callback)

client.event.emit( event, data )

Argument	Type	Optional	Description
event	String	false	An eventname
data	Mixed	true	Any serialisable data ( Objects, Strings, Numbers… ) that will be sent with the event

Sends the event to all subscribed clients

// Client B
client.event.emit('notifications', 'Maria just came online')

client.event.listen( pattern, callback )

Argument	Type	Optional	Description
pattern	String (regex)	false	The pattern to match events which subscription status you want to be informed of
callback	Function	false	A function that will be called whenever an event matching the `pattern` has been initially subscribed to. When there are no more subscriptions to any events matching `pattern`, the callback passed to `response.onStop()` is called. Arguments are (String) match, and response (Object)

Registers the client as a listener for event subscriptions made by other clients. This is useful to create active data providers - processes that only send events if clients are actually interested in them. You can find more about listening in the events tutorial.

The callback is invoked with two arguments:

match: the name of the event that has been matched against the provided pattern
response: contains two functions (accept and reject), one of them needs to be called

client.event.listen('^news/.*', (match, response) => {
  // see tutorial for more details
})

client.event.unlisten( pattern )

Argument	Type	Optional	Description
pattern	String (regex)	false	he previously registered pattern

This removes a previously registered listening pattern and the user will no longer be listening for active/inactive subscriptions.

client.event.unlisten('^news/.*')