@onehilltech/blueprint/lib/messaging/listener.js

lightweight, simple, elegant framework for building mean applications

/*
 * Copyright (c) 2018 One Hill Technologies, LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

const assert = require ('assert');
const { BO } = require ('base-object');

/**
 * @class Listener
 *
 * Base class for all listener objects in the Blueprint framework. A listener is
 * an object type can handle messages from other components, such as Controller,
 * Service, Router, etc.
 *
 * All listeners must implement the handleEvent() method.
 *
 * Listener objects are added to the framework in by exporting the class from a
 * file located in app/listeners. The name of the directory defines the event the
 * listener handles, and the name of the file defines the name of the listener.
 */
module.exports = BO.extend ({
  /**
   * Event handler for the listener. The number of arguments will depend on the
   * number of arguments passed to the emit() method.
   */
  handleEvent: null,

  init () {
    this._super.call (this, ...arguments);

    assert (!!this.handleEvent, 'The subclass must implement the handleEvent() method');
  }
});