Signals

Signals

Signals components are used to listen to global messages.

An object with a Signals component can listen to messages sent from anywhere by declaring handlers for them.

DOM events that have no node targets are broadcast as signals. These events include Window events, like onload and onbeforeunload, and events that occur directly on document, like onkeypress if document has the focus. Setting the on<MessageName> property to the name of an owner method causes that method to be called when on<MessageName> is broadcast, for any <MessageName>. For example:

enyo.kind({
    name: "Receiver",
    components: [
        // 'onTransmission' is the message name and 'transmission' is the
        // name of a handler method in my owner.
        {kind: "Signals", onTransmission: "transmission"}
    ],
	transmission: function(inSender, inPayload) {
	}
});

Note that, like all Enyo message handlers, the signal handler (transmission) receives two parameters: a reference to the component that sent the message (in this case, our own Signals object, this.$.signals), and any payload the transmitter included in the broadcast.

To broadcast a message, call send, a static method on the enyo.Signals kind:

enyo.kind({
    name: "Sender",
    transmit: function(inPayload) {
        enyo.Signals.send("onTransmission", inPayload);
    }
});

Important Notes

• The signal name passed into send must exactly match the message name in the receiver Signals instance; both must include the on prefix.

• All Signals instances that register a handler for a particular message name will receive the message.

• The send method is on the enyo.Signals kind itself, not an instance of a Signals component.

Do not abuse Signals. Coupling objects with global communication is considered evil.