前言，关于Lightning Message Channel

大家可能会经常听到Pub/Sub通信模式。

在Salesforce上面，如果我们要用到Pub/Sub通信模式，那么最简单的就是使用Lightning Message Channel。

要用Lightning Message Channel之前，我们需要做一些准备工作，去定义messageChannels的内容，然后部署到Salesforce环境上面。

定义messageChannels.xml文件

如果我们要传递recordId和recordData，那么我们就需要定义如下的XML文件

<?xml version="1.0" encoding="UTF-8"?>
<LightningMessageChannel xmlns="http://soap.sforce.com/2006/04/metadata">
    <isExposed>true</isExposed>
    <lightningMessageFields>
        <fieldName>recordId</fieldName>
    </lightningMessageFields>
    <lightningMessageFields>
        <fieldName>recordData</fieldName>
    </lightningMessageFields>
    <masterLabel>Sample Message Channel</masterLabel>
</LightningMessageChannel>

publisherComponent.cmp

<aura:component implements="force:appHostable,flexipage:availableForAllPageTypes,flexipage:availableForRecordHome,force:hasRecordId,forceCommunity:availableForAllPageTypes,force:lightningQuickAction" access="global" >
    <lightning:button label="Send Payload" onclick="{! c.handleClick }"/>
    <lightning:messageChannel type="SampleMessageChannel__c"
            aura:id="sampleMessageChannel"/>
</aura:component>

publisherComponentController.js

// publisherController.js
({
    handleClick: function(cmp, event, helper) {
        var payload = {
            recordId: "some string",
            recordData: {
    value: "some value"
}
        };

        cmp.find("sampleMessageChannel").publish(payload);
    }
})

subscriberComponent.cmp

<aura:component implements="force:appHostable,flexipage:availableForAllPageTypes,flexipage:availableForRecordHome,force:hasRecordId,forceCommunity:availableForAllPageTypes,force:lightningQuickAction" access="global" >
	  <aura:attribute name="recordValue" type="String"/>
    <lightning:formattedText value="{!v.recordValue}" />
    <lightning:messageChannel type="SampleMessageChannel__c"
            onMessage="{!c.handleChanged}" scope="APPLICATION"/>
</aura:component>

subscriberComponentController.js

// subscriberController.js
({
    handleChanged: function(cmp, message, helper) {
        // Read the message argument to get the values in the message payload
    if (message != null && message.getParam("recordData") != null) {
        cmp.set("v.recordValue", message.getParam("recordData").value);
    }
    }
})

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