Application Event
Pubsub js
/**
* A basic pub-sub mechanism for sibling component communication
*
* TODO - adopt standard flexipage sibling communication mechanism when it's available.
*/
const events = {};
const samePageRef = (pageRef1, pageRef2) => {
const obj1 = pageRef1.attributes;
const obj2 = pageRef2.attributes;
return Object.keys(obj1)
.concat(Object.keys(obj2))
.every(key => {
return obj1[key] === obj2[key];
});
};
/**
* Registers a callback for an event
* @param {string} eventName - Name of the event to listen for.
* @param {function} callback - Function to invoke when said event is fired.
* @param {object} thisArg - The value to be passed as the this parameter to the callback function is bound.
*/
const registerListener = (eventName, callback, thisArg) => {
// Checking that the listener has a pageRef property. We rely on that property for filtering purpose in fireEvent()
if (!thisArg.pageRef) {
throw new Error(
'pubsub listeners need a "@wire(CurrentPageReference) pageRef" property'
);
}
if (!events[eventName]) {
events[eventName] = [];
}
const duplicate = events[eventName].find(listener => {
return listener.callback === callback && listener.thisArg === thisArg;
});
if (!duplicate) {
events[eventName].push({ callback, thisArg });
}
};
/**
* Unregisters a callback for an event
* @param {string} eventName - Name of the event to unregister from.
* @param {function} callback - Function to unregister.
* @param {object} thisArg - The value to be passed as the this parameter to the callback function is bound.
*/
const unregisterListener = (eventName, callback, thisArg) => {
if (events[eventName]) {
events[eventName] = events[eventName].filter(
listener =>
listener.callback !== callback || listener.thisArg !== thisArg
);
}
};
/**
* Unregisters all event listeners bound to an object.
* @param {object} thisArg - All the callbacks bound to this object will be removed.
*/
const unregisterAllListeners = thisArg => {
Object.keys(events).forEach(eventName => {
events[eventName] = events[eventName].filter(
listener => listener.thisArg !== thisArg
);
});
};
/**
* Fires an event to listeners.
* @param {object} pageRef - Reference of the page that represents the event scope.
* @param {string} eventName - Name of the event to fire.
* @param {*} payload - Payload of the event to fire.
*/
const fireEvent = (pageRef, eventName, payload) => {
if (events[eventName]) {
const listeners = events[eventName];
listeners.forEach(listener => {
if (samePageRef(pageRef, listener.thisArg.pageRef)) {
try {
listener.callback.call(listener.thisArg, payload);
} catch (error) {
// fail silently
}
}
});
}
};
export {
registerListener,
unregisterListener,
unregisterAllListeners,
fireEvent
};
pubComp
<template>
<lightning-button label="call Event" onclick={callEvent}></lightning-button>
</template>
JS
import { LightningElement, wire ,track} from 'lwc';
import{CurrentPageReference} from 'lightning/navigation';
import{fireEvent} from 'c/pubsub';
export default class PubComp extends LightningElement {
@wire(CurrentPageReference) pageRef;
callEvent(event){
var eventParam={'firstname':'Vinayak'};
fireEvent(this.pageRef,'pubsubevent',eventParam);
}
}
SubComponent
JS
import { LightningElement, wire } from 'lwc';
import{registerListener,unregisterAllListeners} from 'c/pubsub';
import{CurrentPageReference} from 'lightning/navigation';
export default class SubComp extends LightningElement {
@wire(CurrentPageReference) pageRef;
connectedCallback(){
registerListener('pubsubevent',this.handleCallback,this);
}
disconnectedCallback(){
unregisterAllListeners(this);
}
handleCallback(detail)
{
alert('parameter from publicsher'+detail.firstname);
}
}
O.p
When Clicked on component(PubComp) that is firing event on
button click(SubComp) then its pop’s a message as alert(From Sub Comp) parameter
from publicsherVinayak
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