Entities provide object-oriented abstractions for data and allow for extending functionality through inheritance and middleware hooks. Key features include: - Extending from EventEmitter for event handling - CRUD methods like create, read, update, and delete - Before, after, and last hooks for adding middleware like validation - Ability to extend entities for additional methods and inheritance - Options to connect entities to data sources like MongoDB through adapters Entities aim to abstract data access, inheritance, and middleware handling for building robust data models and APIs.

1. Entities on Node.jsEntities on Node.js

2. /thanpolas/entity/thanpolas/entity

3. Entities useEntities use
CIP
​for Classical Inheritance
/thanpolas/cip
Bluebird
for the 100% Promises API
/petkaantonov/bluebird
Middlewarify
for creating middleware
/thanpolas/middlewarify

4. Entities extendEntities extend
events.EventEmitter
...and that's the only thing they do

5. Creating an EntityCreating an Entity
var entity = require('entity');
var EntityChild = entity.extend(function() {
this.a = 1;
});
var EntityGrandChild = EntityChild.extend();
entity.extend
var entity = require('entity');
var UserEntity = entity.extendSingleton(function() {});
/* ... */
var userEnt = UserEntity.getInstance();
entity.extendSingleton

6. Entities AdaptorsEntities Adaptors
MongooseMongoose
MongoDB ORM
http://mongoosejs.com/
SequelizeSequelize
PostgreSQL
MySQL
MariaDB
SQLite
http://sequelizejs.com/

7. CRUD PrimitivesCRUD Primitives
create(data)
read(query=)
readOne(query)
readLimit(?query, offset, limit)
update(query, updateValues)
delete(query)
count(query=)

8. CRUD PrimitivesCRUD Primitives
create()create()
entity.create({name: 'thanasis'})
.then(function(udo) {
udo.name === 'thanasis'; // true
})
.catch(function(error) {
// deal with error.
});
... so on and so forth ...

9. Entity HooksEntity Hooks
Middlewarify in action
before
after
last

10. Entity HooksEntity Hooks
beforebefore
// a middleware with synchronous resolution
entity.read.before(function(data){
if (!data.name) {
throw new TypeError('No go my friend');
}
});
// then...
entity.read({}).then(function(document) {
// you'll never get here
}, function(err) {
err instanceof Error; // true
err.message === 'No go my friend'; // true
});

11. Hooks are FiFoHooks are FiFo
Order MATTERSOrder MATTERS

12. Hooks areHooks are
MiddlewareMiddleware

13. Before HooksBefore Hooks
Get the exact same number or arguments
After & Last HooksAfter & Last Hooks
Gets the result plus the original number or arguments

14. Entity HooksEntity Hooks
AsynchronicityAsynchronicity
entity.create.before(function(data){
return promiseReturningFn(function(result) {
resolve(result + 1);
});
});

15. Extending EntitiesExtending Entities
adding new methodsadding new methods

16. Extending EntitiesExtending Entities
Just use the prototypeJust use the prototype
var Entity = require('entity');
var UserEntity = module.exports = Entity.extend();
UserEntity.prototype.report = function(userId) {
return promiseReturningAction(userId);
};

17. Extending EntitiesExtending Entities
Using method()Using method()
var Entity = require('entity');
var UserEntity = module.exports = Entity.extend(function() {
this.method('report', this._report.bind(this));
this.report.before(this._checkUserId.bind(this));
this.report.after(this._normalize.bind(this));
});
UserEntity.prototype._report = function(userId) {
return promiseReturningAction(userId);
};

18. Let's combine all upLet's combine all up

19. var ClipEntity = module.exports = EntityBase.extendSingleton(function() {
this.setModel(clipModel.Model);
this.method('readOneApi', this.readOne);
this.method('readLimitApi', this.readLimit);
this.method('updateApi', this.update);
this.method('readApi', this.read);
// Apply system wide (global) filters
this.readLimitApi.before(this.systemFilter.bind(this));
this.readOneApi.before(this.systemFilter.bind(this));
// Clip Creation middleware
this.create.before(this._populateActiveEvent.bind(this));
this.create.after(this._processNewClip.bind(this));
// Record sanitization middleware
this.updateApi.after(helpers.skipArgs(this.sanitizeResult, 2, this));
this.readLimitApi.after(helpers.skipArgs(this.sanitizeResults, 3, this));
this.readOneApi.after(helpers.skipArgs(this.sanitizeResult, 1, this));
});
A Production-ish EntityA Production-ish Entity

20. Entity Hands OnEntity Hands On
this.readLimitApi.before(this.systemFilter.bind(this));
/**
* Apply system filters in all incoming READ queries
* to exclude deleted and corrupt items.
*
* @param {Object} query The query.
*/
ClipEntity.prototype.systemFilter = function(query) {
query.notFound = { ne: true };
query.processed = true;
};

21. Entity Hands OnEntity Hands On
this.create.after(this._processNewClip.bind(this));
/**
* Post creation clip processing.
*
* @param {Object} data Item used to create the record.
* @param {app.entity.ClipProcess} processEnt The process entity.
* @param {mongoose.Document} clipItem The result.
* @return {Promise} A promise.
* @private
*/
ClipEntity.prototype._processNewClip = Promise.method(function(data, processEnt,
clipItem) {
processEnt.clipId = clipItem.id;
log.finest('_processNewClip() :: Clip Saved to DB, starting FS save...', clipItem.id);
return this._checkWatermarkAndStore(processEnt, clipItem)
.bind(processEnt)
.then(processEnt.createThumbnail)
.then(processEnt.checkS3)
.then(processEnt.updateDatabase)
.then(function() {
log.fine('_processNewClip() :: Clip processing finished:',
processEnt.sourceFilePath);
})
.catch(processEnt.moveToTrash)
.catch(processEnt._deleteRecord);
});

22. Now let's get crazyNow let's get crazy

23. EntitiesEntities
++
CrudeCrude
POST /user
GET /user
GET /user/:id
PUT /user/:id
PATCH /user/:id
DELETE /user/:id
/thanpolas/crude

24. ... but not today... but not today

25. Thank you
(here is where you applaud)
Thanasis Polychronakis
@thanpolas
http://www.slideshare.net/thanpolas

26. Questions?
Be a critic
Thanasis Polychronakis
@thanpolas
http://www.slideshare.net/thanpolas

27. Shameless Plug Time
Promo Code
bgwebsummit
From 60€ --> 40€
15/5/2015
@ Thessaloniki Greece
devitconf.org

28. Questions?
Thanasis Polychronakis
@thanpolas