Say I want to build an application in which models could have different data sources (like MySQL, some API, XML, etc).
What would be the most common approache(s) in order to implement something like this, and what design patterns would be used?
I think DAO is what you are looking for.
Think like:
interface RdbmsDriver {
public function connect();
public function disconnect();
public function query($sql);
public function fetchAll($sql);
}
class MysqliDriver implements RdbmsDriver {
public function connect() { }
public function disconnect() { }
public function query($sql) { }
public function fetchAll($sql) { }
}
class PgsqlDriver implements RdbmsDriver {
public function connect() { }
public function disconnect() { }
public function query($sql) { }
public function fetchAll($sql) { }
}
abstract class RdbmsDao {
protected $driver;
public function __construct(RdbmsDriver $driver) {
$this->driver = $driver;
}
}
interface SomeEntityDao {
public function insert(SomeEntity entity);
public function update(SomeEntity entity);
public function delete(SomeEntity entity);
public function find($entityKey);
public function findAll();
}
/**
* Data from relational databases.
*/
class SomeEntityRdbmsDao extends RdbmsDao implements SomeEntityDao {
public function insert(SomeEntity entity) { }
public function update(SomeEntity entity) { }
public function delete(SomeEntity entity) { }
public function find($entityKey) { }
public function findAll() { }
}
// Use like: new SomeEntityRdbmsDao(new MysqliDriver(...))
/**
* Data from a webservice
*/
class SomeEntityWebServiceDao implements SomeEntityDao {
public function insert(SomeEntity entity) { }
public function update(SomeEntity entity) { }
public function delete(SomeEntity entity) { }
public function find($entityKey) { }
public function findAll() { }
}
class SomeEntityModel {
private $persistance;
public function __construct(SomeEntityDao $persistance) {
$this->persistance = $persistance;
}
}
I would go with the Data Mapper approach.
The mapper is not restricted to databases, it could handle any datasource (file, db, xml, api etc.)
The most important thing is to have your Domain Model separated from the data source. To make the mapper truly interchangeable can be a hard thing, because the datasources are of a different kind. A XML source is not writeable, so you cannot implement an insert method for example.
Related
I'm using repository pattern in my Laravel project.
what is the good pattern to call service from other service?
For example service will looks like this:
class GetAllUsersService
{
private $userRepository;
public function __construct(UserRepository $repository)
{
$this->userRepository = $repository;
}
public function execute()
{
return $this->userRepository->getAll();
}
}
Now if I want to execute this service from other part of the application I will do something like this:
class AnyClass
{
public function executeUserService()
{
$repository = new UserEloquentRepository();
$service = new GetAllUsersService($repository);
return $service->execute();
}
}
Is it correct way to do it? Is there other ways? Maybe some UI layer should be in between?
I think you have three ways to do it:
1) use method __construct();
class AnyClass
{
private $get_all_users_service;
public function __construct(GetAllUsersService $get_all_users_service)
{
$this->get_all_users_service = $get_all_users_service;
}
public function index()
{
$fetchAllUsers = $this->get_all_users_service->fetchAll();
}
}
2) use the specified services like a parameter of each function needs to use them:
class AnyClass
{
public function index(GetAllUsersService $get_all_users_service)
{
$fetchAllUsers = $get_all_users_service->fetchAll();
}
}
3) use method app() of Laravel helper like this:
class AnyClass
{
public function index()
{
$get_all_users_service = app(GetAllUsersService::class);
$fetchAllUsers = $get_all_users_service->fetchAll();
}
}
I have a problem with an error I am getting that says:
Class Car contains 1 abstract method and must therefore be decla
red abstract or implement the remaining methods (Car::accelerate) in C:\xampp
\htdocs\php\learn_php_oop\Car.php on line 58.
This is the code in two files I am using:
Car.php
<?php
/**
* represents generic properties and methods for any type of car
*/
class Car
{
protected $colour, $doorNumber, $fuelType, $rightHandDrive, $accelerate;
public function __construct($rightHandDrive = true)
{
$this->rightHandDrive = $rightHandDrive;
}
public function getColour()
{
return $this->colour;
}
public function setColour($colour)
{
$this->colour = $colour;
}
public function getDoorNumber()
{
return $this->doorNumber;
}
public function setDoorNumber($doorNumber)
{
$this->doorNumber = $doorNumber;
}
public function getFuelType()
{
return $this->fuelType;
}
public function setFuelType($fuelType)
{
$this->fuelType = $fuelType;
}
public function getRightHandDrive()
{
return $this->rightHandDrive;
}
public function setRightHandDrive($rightHandDrive)
{
$this->rightHandDrive = $rightHandDrive;
}
abstract protected function accelerate();
}
?>
Sport_car.php
<?php
include ('Car.php');
/**
* represents sport cars
*/
class Sport_car extends Car
{
public function accelerate()
{
$this->accelerate = 5;
}
}
?>
I have spent some time trying to figure out why this is happening but I just do not know why? Please help.
It's an OOP problem, in your case you must declare your Car Object as Abstract like this :
<?php
/**
* represents generic properties and methods for any type of car
*/
abstract class Car
{
protected $colour, $doorNumber, $fuelType, $rightHandDrive, $accelerate;
public function __construct($rightHandDrive = true)
{
$this->rightHandDrive = $rightHandDrive;
}
public function getColour()
{
return $this->colour;
}
public function setColour($colour)
{
$this->colour = $colour;
}
public function getDoorNumber()
{
return $this->doorNumber;
}
public function setDoorNumber($doorNumber)
{
$this->doorNumber = $doorNumber;
}
public function getFuelType()
{
return $this->fuelType;
}
public function setFuelType($fuelType)
{
$this->fuelType = $fuelType;
}
public function getRightHandDrive()
{
return $this->rightHandDrive;
}
public function setRightHandDrive($rightHandDrive)
{
$this->rightHandDrive = $rightHandDrive;
}
abstract protected function accelerate();
}
?>
Explanations :
A class wich is extended with at least one abstract method in it has to be defined as abstract itself, otherwise you'll get an error
I have a class that is using the State pattern. Here's a simple example
/**
* #Enitity
**/
class Door
{
protected $id;
protected $state;
public function __construct($id, DoorState $state)
public function setState(DoorState $state)
{
$this->state = $state;
}
public function close()
{
$this->setState($this->state->close())
}
...
}
interface DoorState
{
public function close;
public function open;
public function lock;
public function unlock;
}
class DoorAction implements DoorState
{
public function close()
{
throw new DoorError();
}
...
}
then several classes that define the appropriate actions in the states
class OpenedDoor extends DoorAction
{
public function close()
{
return new ClosedDoor();
}
}
So I would have some thing like
$door = new Door('1', new OpenedDoor());
DoctrineDoorRepository::save($door);
$door->close();
DoctrineDoorRepository::save($door);
How would I implement the mapping in Doctrine so I can persist it?
I'm hung up on the $state property. I would like to save the whole DoorAction based object but do I have to the map the DoorAction super class or each individual sub class?
I've looked at implementing it using Embeddable or SuperMapping but run into problems with each.
Doctrine2 DBAL has a feature in the documentation that allows ENUM's
https://www.doctrine-project.org/projects/doctrine-orm/en/current/cookbook/mysql-enums.html#mysql-enums
When we take the Solution 2: Defining a Type as a base, one could create an own type, for instance called doorstatetype or similar to represent the open/closed state. For instance like this:
<?php
namespace Acme\Model\Door;
use Doctrine\DBAL\Types\Type;
use Doctrine\DBAL\Platforms\AbstractPlatform;
class DoorStateType extends Type
{
const ENUM_DOORSTATE = 'enumdoorstate';
const STATE_OPEN = 'open';
const STATE_CLOSED = 'closed';
public function getSQLDeclaration(array $fieldDeclaration, AbstractPlatform $platform)
{
return "ENUM('" . self::STATE_OPEN . "', '" . self::STATE_CLOSED . "') COMMENT '(DC2Type:" . ENUM_DOORSTATE . ")'";
}
public function convertToPHPValue($value, AbstractPlatform $platform)
{
return $value;
}
public function convertToDatabaseValue($value, AbstractPlatform $platform)
{
if (!in_array($value, array(self::STATE_OPEN, self::STATE_CLOSED))) {
throw new \InvalidArgumentException("Invalid state");
}
return $value;
}
public function getName()
{
return self::ENUM_DOORSTATE;
}
}
And then use it like this:
<?php
namespace Acme\Model\Door;
/** #Entity */
class Door
{
/** #Column(type="enumdoorstate") */
private $state;
public function open()
{
if (!DoorStateType::STATE_OPEN === $this->state) {
throw new \LogicException('Cannot open an already open door');
}
$this->state = DoorStateType::STATE_OPEN;
}
public function close()
{
if (!DoorStateType::STATE_CLOSED === $this->state) {
throw new \LogicException('Cannot close an already closed door');
}
$this->state = DoorStateType::STATE_CLOSED;
}
}
This allows searching for states:
$openDoors = $repository->findBy(array('state' => DoorStateType::STATE_OPEN));
You could basically then have the convertToPHPValue method create objects of the desired states that allow for some logic, like checking if an open door can be locked or similar.
In the case where the state has to be a class that contains logic, you could implement it like this:
First we define a normal state from which we can inherit:
<?php
namespace Acme\Model\Door;
abstract class DoorState
{
// Those methods define default behaviour for when something isn't possible
public function open()
{
throw new \LogicException('Cannot open door');
}
public function close()
{
throw new \LogicException('Cannot close door');
}
abstract public function getStateName();
}
Then the OpenState:
<?php
namespace Acme\Model\Door;
class OpenState extends DoorState
{
const STATE = 'open';
public function close()
{
return new ClosedState();
}
public function getStateName()
{
return self::STATE;
}
// More logic
}
And finally the ClosedState:
<?php
namespace Acme\Model\Door;
class ClosedState extends DoorState
{
const STATE = 'closed';
public function open()
{
return new OpenState();
}
public function getStateName()
{
return self::STATE;
}
// More logic
}
We can then, for persistence, simply use different convert methods:
<?php
namespace Acme\Model\Door;
use Doctrine\DBAL\Types\Type;
use Doctrine\DBAL\Platforms\AbstractPlatform;
class DoorStateType extends Type
{
// SQL declarations etc.
public function convertToPHPValue($value, AbstractPlatform $platform)
{
if ($value === OpenState::STATE) {
return new OpenState();
}
if ($value === ClosedState::STATE) {
return new ClosedState();
}
throw new \Exception(sprintf('Unknown state "%s", expected one of "%s"', $value, implode('", "', [OpenState::STATE, ClosedState::STATE])));
}
public function convertToDatabaseValue($value, AbstractPlatform $platform)
{
return $value->getStateName();
}
}
What if you map state as a string and then:
public function setState(DoorState $state)
{
$this->state = serialize($state);
}
and:
private function state()
{
return unserialize($this->state);
}
public function close()
{
$this->setState($this->state()->close())
}
It doesn't save my changes after adding a category.
If I add a category, it is seen in the overview, but if I refresh I see the original amount.
I guess there is an error in my Singleton-design but I can't seem to find it.
class ProductService {
private $_database;
public function __construct($databaseType) {
$databaseFactory = new DatabaseFactory();
$this->_database = $databaseFactory->createDatabase($databaseType);
}
public function addCategory($category){
$this->_database->addCategory($category);
}
public function getAllCategories() {
return $this->_database->getAllCategories();
}
}
class DatabaseFactory {
public function __construct() {
}
public function createDatabase($type){
switch ($type) {
case "Memory" :
return MemoryDatabase::getInstance();
}
}
}
class MemoryDatabase {
private $categories;
private function __construct() {
$this->categories = array(
new Category("Cheese"),
);
}
public static function getInstance() {
static $inst = null;
if ($inst === null) {
$inst = new MemoryDatabase();
}
return $inst;
}
private function __clone() {}
private function __wakeup() {}
public function addCategory($category) {
array_push($this->categories, $category);
}
public function getAllCategories() {
return $this->categories;
}
}
Each request you perform in PHP is stateless.
If you want to persist data between requests, you will need to put your data in some form of persistant storage, i.e., sessions, filesystem, database, memory, etc.
Singleton pattern only ensures a single copy of an object is created, for a given request.
I have the following PHP code as chain of resposibility, I am using PHP5.4.9.
abstract class Logger
{
protected $next;
public function next($next)
{
$this->next = $next;
return $this->next;
}
public function run(){
$this->invoke();
if(null!=$this->next){
$this->next->invoke();
}
}
abstract public function invoke();
}
class EmailLogger extends Logger
{
public function invoke()
{
print_r("email\n");
}
}
class DatabaseLogger extends Logger
{
public function invoke()
{
print_r("database\n");
}
}
class FileLogger extends Logger
{
public function invoke()
{
print_r("file \n");
}
}
$logger = new EmailLogger();
$logger->next(new DatabaseLogger())->next(new FileLogger());
$logger->run();
the expect output is:
email
database
file
but the actually output:
email
database
I hope to implement chain of resposibility design pattern by PHP language, one abstract class and three or more classes to do something as a chain. but only the first two object works.
Anyting missing? Or PHP can not use this coding style under PHP5.4.9?
Thanks.
Replace
public function run() {
$this->invoke ();
if (null != $this->next) {
$this->next->invoke();
}
}
With
public function run() {
$this->invoke ();
if (null != $this->next) {
$this->next->run ();
}
}
please try $this->next->invoke() change $this->next->run()