Bsrgvty

I have an LWC in which I want to use EMP API. Docs say that's only currently available in Aura. Do I have to wrap my entire LWC in aura in order to add the EMP API, or can I create a utility aura component and do pub-sub to/from the LWC?

Summer 19 is 1 week away, but that won't stop you from preparing it beforehand in your Summer 19 Sandbox or Scratch org.

lightning:empApi does not show LWC button as enabled as its referring to the Spring version of docs.

Also , the release notes dont tell us about how to use empAPI in LWC. I could not find any public documentation on about how to use it.

A quick way to refer docs of lwc is Summer 19 org is to visit the url

https://yourSummer19org.salesforce.com/docs/component-library/bundle/lightning-emp-api/documentation

Sample Example :

<template>
 <lightning-card title="EmpApi Example" icon-name="custom:custom14">
 <div class="slds-m-around_medium">
 <p>Use the buttons below to subscribe and unsubscribe to a streaming channel!</p>
 <lightning-input label="Channel Name" value=channelName
 onchange=handleChannelName></lightning-input>
 <lightning-button variant="success" label="Subscribe" title="Subscribe"
 onclick=handleSubscribe disabled=isSubscribeDisabled
 class="slds-m-left_x-small"></lightning-button>
 <lightning-button variant="destructive" label="Unsubscribe" title="Unsubscribe"
 onclick=handleUnsubscribe disabled=isUnsubscribeDisabled
 class="slds-m-left_x-small"></lightning-button>
 </div>
 </lightning-card>
</template>

JS:

import LightningElement, track from 'lwc';
import subscribe, unsubscribe, onError, setDebugFlag, isEmpEnabled from 'lightning/empApi';

export default class EmpApiLWC extends LightningElement 
 @track channelName = '/event/Test__e';
 @track isSubscribeDisabled = false;
 @track isUnsubscribeDisabled = !this.isSubscribeDisabled;

 subscription = ;

 // Tracks changes to channelName text field
 handleChannelName(event) 
 this.channelName = event.target.value;
 

 // Handles subscribe button click
 handleSubscribe() 
 // Callback invoked whenever a new event message is received
 const messageCallback = function(response) 
 console.log('New message received : ', JSON.stringify(response));
 // Response contains the payload of the new message received
 ;

 // Invoke subscribe method of empApi. Pass reference to messageCallback
 subscribe(this.channelName, -1, messageCallback).then(response => 
 // Response contains the subscription information on successful subscribe call
 console.log('Successfully subscribed to : ', JSON.stringify(response.channel));
 this.subscription = response;
 this.toggleSubscribeButton(true);
 );
 

 // Handles unsubscribe button click
 handleUnsubscribe() 
 this.toggleSubscribeButton(false);

 // Invoke unsubscribe method of empApi
 unsubscribe(this.subscription, response => 
 console.log('unsubscribe() response: ', JSON.stringify(response));
 // Response is true for successful unsubscribe
 );
 

 toggleSubscribeButton(enableSubscribe) 
 this.isSubscribeDisabled = enableSubscribe;
 this.isUnsubscribeDisabled = !enableSubscribe;
 

 registerErrorListener() 
 // Invoke onError empApi method
 onError(error => 
 console.log('Received error from server: ', JSON.stringify(error));
 // Error contains the server-side error
 );
 

How about option 3: Wait a week.

According to the release notes, EmpApi is currently slated to go live in LWC for Summer 19.