Inter-Widget Communication (IWC)

Intents API Reference Action: broadcast(nodeValue)

  • nodeValue: Object - the data to be broadcasted to all matching handlers.

Applies to only the Intents API

Broadcast an intent to be Handled by all IWC Intent Registration

When a widget wants to offload operations to other widgets on the bus, intent invocations are used. Much like Android intents, a payload is not a requirement to send with the intent but is an added benefit. Intents can be used for notifications (broadcast to all widgets on the bus), triggering some background operation (shutdown utilities), offloading common tasks (visualizing data, compiling output files, converting documents), and much more.

To invoke an intent onto all handlers, the broadcast action is used:

var jsonRef = iwc.intents.Reference("/application/view/json");
var payload = {
    "Hello": "World!"
};

jsonRef.broadcast(payload).then(function(res){
    // resolves when all of the handlers have handled the intent request.
    // resolves with an array of results
});

Additionally, a callback can be added as a 3rd parameter to watch the status of the intent. The callback acts just as it does for the invoke action, except status updates are received for every handler.

The callback receives 2 parameters:

  1. reply: contains various information about an intent. For the introductory purposes of intent registrations, only reply.entity is covered here, other properties will be covered for more advanced intents in a later tutorial.
  2. done: A function to call to stop handling intent requests. Useful for conditionally stopping intent handling.
property type description
entity Object Data pertaining to the state of the intent.
entity.handler Object Data pertaining to the IWC client handling the request.
entity.handler.address String The address of the handling IWC client.
entity.handler.reason String The reason for this handler being used("onlyOne", "userSelected", or "remembered"
entity.handler.resource String The resource path of the handler function.
entity.request * The data passed to the IWC in the invoke request.
entity.response * The data returned from the handler when finished computing (only available if state is "complete").
entity.state String The state of the intent handling explained in table below.
entity.status String Will be "ok" if this callback is reachable (internal use).

The broadcast promise resolves with a formatted entity of handler responses. The overall format of res above matches that of any other IWC message packet, but res.entity contains a map of results, where the key is the handler resource name and the value is the result returned by the handler's function.

What if there are no handlers?

If there are no handlers open for the desired intent invocation, the invoke promise will reject with a response of "noResource". At current state of the platform, launching a registered application to handle an intent invocation has not been implemented.

It is planned to replace the promise rejection with giving the user a choice of registered applications to launch to handle the desired invocation.