Manageable

A minimal implementation of a manageable object.

What?

A manageable object is any object that can initialize and destroy itself along with its dependencies. It does so by responding to initialize and destroy messages.

Why?

I often find myself writing code like this:

const myService = {
  initialized: false,
  initialize(options) {
    if (initialized) // throw already initialized.
 
    return Promise.all(
      this.dependencies.map(d => d.initialize(options))
    );
  },
  destroy(options) {
    if (!initialized) // throw not initialized.
 
    return Promise.all(
      this.dependencies.map(d => d.destroy(options))
    );
  }
};

So I decided to abstract it into a factory use it like this:

const createManageable = require('./');
 
const myServiceDependencies 
const myService = Object.assign(
  {},
  createManageable({ dependencies: myServiceDependencies })
);
 
// Alternatively
const destroyMyService = function* () {};
const initializeMyService = function* () {};
 
const myService = Object.assign(
  {},
  createManageable({ initialize: initializeMyService, destroy: destroyMyService })
);

If it sounds like over-kill to you, this real world example might show how its useful:

const mongodb = require('mongodb');
 
function createMongoDbClient(options) {
  const { connectionUri } = options;
 
  let db;
 
  const client = Object.assign({
    // Just a test method.
    getDbStats() {
      return db.stats();
    }
  }, createManageable({ initialize: initializeClient, destroy: destroyClient }));
 
  function initializeClient() {
    return mongodb.MongoClient.connect(connectionUri);
  }
 
  function destroyClient() {
    return db.close();
  }
}
 
const myMongoDbClient = createMongoDbClient({
  connectionUri: 'mongodb://localhost/test',
});
 
// Usage with promises
myMongoDbClient
.initialize()
.then(myMongoDbClient.getDbStats())
.then(dbStats => console.log(dbStats))
.then(myMongoDbClient.destroy());
 
// Usage with generators
// assuming `const coroutine = require('co')`;
coroutine(function* () {
  yield myMongoDbClient.intialize();
 
  const dbStats = yield myMongoDbClient.getDbStats();
 
  console.log(dbStats);
 
  yield myMongoDbClient.destroy();
});