Playdoh Modelling Your Objects

7/31/2019 Playdoh Modelling Your Objects

1/42

All rights reserved. Zend Technologies, Inc.

Architecting Your ModelsMatthew Weier O'PhinneyProject LeadZend Framework


2/42

2 All rights reserved. Zend Technologies, Inc.

Goals


3/42


Learn to recognize why old habits may be bad Learn several design patterns that can help

you write testable, maintainable code

Learn some techniques for altering existingbehavior without rewriting existing code


4/424 All rights reserved. Zend Technologies, Inc.

What We've Learned and What We Do



Oooh! Let's create the schema!



Write code that uses the DB



Plain Old Mysql (POM) ActiveRecord

Table/Row Data Gateway



And then


9/42


We start lamenting about performance. We end up refactoring for every new feature

(e.g. caching, logging).

We need to go to a Service OrientedArchitecture, and effectively refactor twice.


10/42


STOPTHE

MADNESS!


11/42


Step One


12/42


Models are just classes.

Create classes.


13/42


Models have metadata and behavior;

createproperties and methods.


14/42


class Person implements PersonInterface{

// Metadataprotected $_email;protected $_password;protected $_username;

// Cheat: use overloading to

// provide setters/getterspublic function __get($name) { }public function __set($name, $value) { }

// Behaviors

public function authenticate() { }public function logout() { }public function ban() { }

}

classPerson implements PersonInterface{ // Metadata

protected$_email;protected$_password;protected$_username;

// Cheat: use overloading to

// provide setters/getterspublicfunction__get($name) { }publicfunction__set($name,$value) { }

// Behaviors

publicfunctionauthenticate() { }publicfunctionlogout() { }publicfunctionban() { }

}


15/42


Step Two


16/42


Nowstart thinking

about datapersistence.


17/42


Identify what data you need to persist Identify how you'll persist the data

Write code for persisting data

(Data Access Layer)


18/42


CREATE TABLE person(usernameVARCHARPRIMARY KEY,passwordVARCHAR,emailVARCHAR,

);

CREATE TABLEperson(usernameVARCHARPRIMARY KEY,passwordVARCHAR,emailVARCHAR,

);

class PersonTableextends Zend_Db_Table_Abstract

{

protected $_name = 'person';protected $_primary = 'username';}

classPersonTableextendsZend_Db_Table_Abstract

{protected$_name='person';protected$_primary='username';

}


19/42


Step Three


20/42


Map your model

to your data.


21/42


Common approaches

Transaction Script (can even use POM) Table Module (often with ActiveRecord or Table

Data Gateway)

Data Mapper / ORM


22/42


class PersonMapperimplements PersonMapperInterface

{

public function save(PersonInterface $person){

$data = array('username' => $person->username,'password' => $person->password,

'email' => $person->email,);

$this->getTable()->save($data);}

public function fetch($username);public function getTable();public function setTable($table);

}

classPersonMapperimplements PersonMapperInterface

{

publicfunctionsave(PersonInterface$person) { $data=array( 'username'=>$person->username, 'password'=>$person->password,

'email' =>$person->email, ); $this->getTable()->save($data); }

publicfunctionfetch($username);publicfunctiongetTable();publicfunctionsetTable($table);

}


23/42


Some notes:

Data !== Relational Database. Data could come from a document database,

filesystem, cache, or web service.

Choose an ORM that allows you to generateyour schema from your entities; allows you toeasily model first, and persistence comes forfree.


24/42


Step Four


25/42


Move business andapplication logic to

a Service Layer.


26/42


Applicationsare like onions;

they have layers.

Photo 2008, MikeChaput-Branson


27/42


The Service Layerprovides application logicon top of your models


28/42


Service Layerin perspective

Data Access Objectsand Data store(s)

Data Mappers

Domain Models

ServiceLayer


29/42


Benefits to a Service Layer

Allows easy consumption of the applicationvia your MVC layer

Allows easy re-use of your applicationvia services

Write CLI scripts that consume theService Layer


30/42


What kind of application logic?

Validation and filtering Authentication and Authorization

Transactions and interactions between model

entities


31/42


class PersonService{

public function create(array$data){

$person = new Person(); if (!$data = $this->getValidator()

->isValid($data)) {

throw new InvalidArgumentException();}

$person->username = $data['username']; $person->password = $data['password']; $person->email = $data['email'];

$this->getMapper()->save($person); return$person;

}}

classPersonService{

publicfunctioncreate(array$data)

{ $person=newPerson(); if(!$data=$this->getValidator()

->isValid($data)) {

throw newInvalidArgumentException(); } $person->username=$data['username']; $person->password=$data['password']; $person->email =$data['email'];

$this->getMapper()->save($person); return$person; }}


32/42


Decorating forfun and profit


33/42


Decorators allow youto add or alter functionalityof an existing class.


34/42


Typical decorators

Implement the same interface(s) of the classbeing decorated

Often use overloading to proxy to thedecorated class

Override specific behavior(s) you wish tomodify or enhance

Add new behaviors that use existing behaviorsin the decorated class


35/42


Refactor to add caching?No!Decorate!

class CachingPersonMapper

classCachingPersonMapper


36/42


class CachingPersonMapperimplements PersonMapperInterface

{public function __construct(

PersonMapperInterface $mapper) { $this->_mapper = $mapper;

}

public function fetch($username) {

$cache = $this->getCache(); if (!$person = $cache->load($username)) { $person = $this->_mapper

->fetch($username); $cache->save($person, $username);

} return$person;

}}

g ppimplements PersonMapperInterface

{publicfunction__construct(

PersonMapperInterface$mapper){ $this->_mapper=$mapper; }

publicfunctionfetch($username){

$cache=$this->getCache(); if(!$person=$cache->load($username)) { $person=$this->_mapper

->fetch($username); $cache->save($person,$username);

} return$person; }}


37/42


Refactor to provide alternatereturn formats? (e.g., JSON, XML, etc.)No!Decorate!

l i l f


38/42


class JsonPerson implements PersonInterface{

public function __construct(

PersonInterface $person ) { $this->_person = $person;

}

public function __toString(){

$data = array('username' => $this->_person->username,'email' => $this->_person->email,

); return json_encode($data);}

}

classJsonPerson implements PersonInterface{

publicfunction__construct(

PersonInterface$person ){ $this->_person=$person; }

publicfunction__toString() { $data=array( 'username'=>$this->_person->username, 'email' =>$this->_person->email, ); returnjson_encode($data); }}


39/42


Nicely FormedObjects


40/42


Rebuilding and refactoring is costly and painful Good OOP and encapsulation CAN make your

life easier

Testing is easier than debugging Choose a good ORM to expedite development.

(Doctrine, Object Freezer, Zend_Entity, etc.)


41/42


Think beyondthe DB!


42/42


Thank you! Feedback: http://joind.in/918

Twitter: @weierophinney

Blog: http://weierophinney.net/matthew/

Documents

Playdoh Modelling Your Objects