@loopback/boot/src/booters/lifecyle-observer.booter.ts

// Copyright IBM Corp. and LoopBack contributors 2018,2020. All Rights Reserved.
// Node module: @loopback/boot
// This file is licensed under the MIT License.
// License text available at https://opensource.org/licenses/MIT

import {
  Application,
  config,
  Constructor,
  CoreBindings,
  inject,
  isLifeCycleObserverClass,
  LifeCycleObserver,
} from '@loopback/core';
import debugFactory from 'debug';
import {BootBindings} from '../keys';
import {ArtifactOptions, booter} from '../types';
import {BaseArtifactBooter} from './base-artifact.booter';

const debug = debugFactory('loopback:boot:lifecycle-observer-booter');

type LifeCycleObserverClass = Constructor<LifeCycleObserver>;

/**
 * A class that extends BaseArtifactBooter to boot the 'LifeCycleObserver' artifact type.
 *
 * Supported phases: configure, discover, load
 *
 * @param app - Application instance
 * @param projectRoot - Root of User Project relative to which all paths are resolved
 * @param bootConfig - LifeCycleObserver Artifact Options Object
 */
@booter('observers')
export class LifeCycleObserverBooter extends BaseArtifactBooter {
  observers: LifeCycleObserverClass[];

  constructor(
    @inject(CoreBindings.APPLICATION_INSTANCE)
    public app: Application,
    @inject(BootBindings.PROJECT_ROOT) projectRoot: string,
    @config()
    public observerConfig: ArtifactOptions = {},
  ) {
    super(
      projectRoot,
      // Set LifeCycleObserver Booter Options if passed in via bootConfig
      Object.assign({}, LifeCycleObserverDefaults, observerConfig),
    );
  }

  /**
   * Uses super method to get a list of Artifact classes. Boot each file by
   * creating a DataSourceConstructor and binding it to the application class.
   */
  async load() {
    await super.load();

    this.observers = this.classes.filter(isLifeCycleObserverClass);
    for (const observer of this.observers) {
      debug('Bind life cycle observer: %s', observer.name);
      const binding = this.app.lifeCycleObserver(observer);
      debug('Binding created for life cycle observer: %j', binding);
    }
  }
}

/**
 * Default ArtifactOptions for DataSourceBooter.
 */
export const LifeCycleObserverDefaults: ArtifactOptions = {
  dirs: ['observers'],
  extensions: ['.observer.js'],
  nested: true,
};