Subscribe to a Message Channel

In this example, we define an Aura component called myNewComponent that contains the custom message channel, SampleMessageChannel__c. The lightning:messageChannel component's onMessage attribute is set to the expression "{!c.handleChanged}", which registers the listener handleChanged.

1<!-- myNewComponent.cmp -->
2<aura:component>
3    <aura:attribute name="recordValue" type="String"/>
4    <lightning:formattedText value="{!v.recordValue}" />
5    <lightning:messageChannel type="SampleMessageChannel__c"
6         onMessage="{!c.handleChanged}"/>
7</aura:component>

1// myNewComponentController.js
2({
3    handleModelChanged: function(cmp, message, helper) { 
4     // Read the message argument to get the values in the message payload
5    if (message != null && message.getParam("recordData") != null) {
6        cmp.set("v.recordValue", message.getParam("recordData").value);
7    }
8  }
9})

Write the handler in your component's controller file. The handleChanged method fires when there is a new message. It checks whether there is a payload in the message, and if so, assigns the new data to the v.recordValue attribute. The lightning:formattedText element updates to display the new value.