caf_pubsub/proxy_pubsub

Proxy that allows a CA to access a publish/subscribe service.

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Extends

Methods

publish(topic, value)

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Publishes a new value for a topic in a pubsub channel.

The channel is implicitly created the first time is used.

There are two types of channels:

  • A personal channel is prefixed by the CA name, i.e., <ca_name>-<whatever>, and only that CA can publish messages.
  • A forum channel has a name of the form forum-<whatever>, and anybody can publish to it.
Parameters:
Name Type Description
topic string

A topic for the published message. It should have a prefix <ca_name>- or forum- depending on the type of channel.
value string

A message to be published.
Throws:

Error If topic has an invalid prefix.

subscribe(topic, methodName)

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Subscribes to a topic.

It also identifies a method name in this CA with signature:

 function(topic:string, value:string, from: string, callback:cbType)
                      or
 async function(topic:string, value:string, from: string)

that will process published events using that topic.

Note that pub/sub notifications use standard messages and standard method ACLs can be applied to restrict publishers.

It is recommended to use an internal method, i.e., one that starts with prefix __ca_. Internal methods are safer because requests always come from the trusted bus and not from external sessions, i.e., the request came from a call to publish() in the app, and not from arbitrary code.

Note that this.$.security.getCallerFrom() does not provide the real caller for internal methods, use the from argument instead.

Parameters:
Name Type Description
topic string

A topic to subscribe.
methodName string

A method name to handle new events of that topic. See the discussion on internal methods above.

unsubscribe(topicopt)

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Unsubscribes from a topic (or all if topic is undefined)

Parameters:
Name Type Attributes Description
topic string <optional>

A topic to unsubscribe (or all topics if undefined).