new ValueStream()
Provides a stream of topic events, specific to the topic selector that this ValueStream was created for, with
topic values provided as instances of the associated DataType.
ValueStream inherits all functions defined on Stream.
Properties:
Name | Type | Description |
---|---|---|
selector |
String | The selector this subscription was created for |
Fires:
- ValueStream#event:open
- ValueStream#event:close
- ValueStream#event:value
- ValueStream#event:subscribe
- ValueStream#event:unsubscribe
- ValueStream#event:error
Examples
// Create a value stream for topic 'foo' session.stream('foo').asType(datatype).on('value', function(topic, specification, newValue, oldValue) { // Receive updates for the topic 'foo' }); // Then subscribe to topic 'foo' session.subscribe('foo');
// Attach multiple listeners for events session.stream('foo').asType(datatype).on({ subscribe : function(topic, specification) { // Subscribed to a particular topic }, unsubscribe : function(topic, specification, reason) { // Unsubscribed from a particular topic }, value : function(topic, specification, newValue, oldValue) { // Value from a topic } });
Extends
Methods
-
close()
-
Close the subscription. No further events will be emitted.
-
off(event, listener) → {Stream}
-
Remove a listener from a specified event.
Parameters:
Name Type Argument Description event
String The event to remove listeners from listener
function <optional>
The listener to remove. All listeners for the event are removed if this is not specified - Inherited From:
Returns:
This stream.- Type
- Stream
Examples
// Bind a single listener to the 'foo' event and then deregister it var listener = function() {}; stream.on('foo', listener); stream.off('foo', listener);
// Bind a listener to the 'foo' event and deregister all listeners var listener = function() {}; stream.on('foo', listener); stream.off('foo');
-
on(events, listener) → {Stream}
-
Register listeners against events.
A single listener may be bound to an event by passing the event name and listener function.
Multiple listeners may be bound by passing in an object, mapping event names to listener functions.
Parameters:
Name Type Argument Description events
String | Object The event name or object mapping event names to listeners listener
function <optional>
The listener to bind to the event, if passed as string. - Inherited From:
Returns:
This stream.- Type
- Stream
Examples
// Bind a single listener to the 'foo' event stream.on('foo', function(arg1, arg2) { console.log("Called for 'foo' event", arg1, arg2); });
// Bind multiple listeners stream.on({ foo : function() { ... }, bar : function() { ... }, baz : function() { ... } });
Events
-
close
-
Emitted when the subscription has been closed using ValueStream#close.
-
error
-
Emitted when the subscription request fails. No further events will be emitted after this.
Properties:
Name Type Description error
ErrorReason the error the subscription request failed with -
open
-
Emitted when the subscription is initially opened, passing a reference to the subscription itself. This will only be fired once.
-
subscribe
-
Emitted when a topic that is selected by this ValueStream's topic selector is subscribed to by this session. Once subscribed,
value
update events may be received for this topic. The specification is a TopicSpecification instance that contains details about the topic.Properties:
Name Type Description topic
String the topic to which the subscription applies specification
diffusion.topics.TopicSpecification instance that contains details about the topic -
unsubscribe
-
Emitted when a topic that was previously subscribed, has been unsubscribed. No further update events will be received from this topic until subscribed again. Unsubscriptions may occur due to the topic being removed, or through calling Session#unsubscribe - an object containing the reason is provided.
Properties:
Name Type Description topic
String the topic to which the unsubscription applies specification
diffusion.topics.TopicSpecification instance that contains details about the topic reason
diffusion.topics.UnsubscribeReason the reason for the unsubscription -
value
-
Emitted when an update has been received for a topic's value. Values will be provided as instances appropriate for the associated DataType this subscription was created for. Both the previous value and the new value are provided.
Properties:
Name Type Description topic
String the topic to which the update applies specification
diffusion.topics.TopicSpecification instance that contains details about the topic newValue
object the new value of the topic oldValue
object the old value of the topic