Adapter em PHP
O Adapter é um padrão de projeto estrutural, que permite a colaboração de objetos incompatíveis.
O Adapter atua como um wrapper entre dois objetos. Ele captura chamadas para um objeto e as deixa reconhecíveis tanto em formato como interface para este segundo objeto.
Complexidade:
Popularidade:
Exemplos de uso: O padrão Adapter é bastante comum no código PHP. É frequentemente usado em sistemas baseados em algum código legado. Nesses casos, os adaptadores criam código legado com classes modernas.
Identificação: O adapter é reconhecível por um construtor que utiliza uma instância de tipo abstrato/interface diferente. Quando o adaptador recebe uma chamada para qualquer um de seus métodos, ele converte parâmetros para o formato apropriado e direciona a chamada para um ou vários métodos do objeto envolvido.
Exemplo conceitual
Este exemplo ilustra a estrutura do padrão de projeto Adapter. Ele se concentra em responder a estas perguntas:
- De quais classes ele consiste?
- Quais papéis essas classes desempenham?
- De que maneira os elementos do padrão estão relacionados?
Depois de aprender sobre a estrutura do padrão, será mais fácil entender o exemplo a seguir, com base em um caso de uso PHP do mundo real.
index.php: Exemplo conceitual
<?php
namespace RefactoringGuru\Adapter\Conceptual;
/**
* The Target defines the domain-specific interface used by the client code.
*/
class Target
{
public function request(): string
{
return "Target: The default target's behavior.";
}
}
/**
* The Adaptee contains some useful behavior, but its interface is incompatible
* with the existing client code. The Adaptee needs some adaptation before the
* client code can use it.
*/
class Adaptee
{
public function specificRequest(): string
{
return ".eetpadA eht fo roivaheb laicepS";
}
}
/**
* The Adapter makes the Adaptee's interface compatible with the Target's
* interface.
*/
class Adapter extends Target
{
private $adaptee;
public function __construct(Adaptee $adaptee)
{
$this->adaptee = $adaptee;
}
public function request(): string
{
return "Adapter: (TRANSLATED) " . strrev($this->adaptee->specificRequest());
}
}
/**
* The client code supports all classes that follow the Target interface.
*/
function clientCode(Target $target)
{
echo $target->request();
}
echo "Client: I can work just fine with the Target objects:\n";
$target = new Target();
clientCode($target);
echo "\n\n";
$adaptee = new Adaptee();
echo "Client: The Adaptee class has a weird interface. See, I don't understand it:\n";
echo "Adaptee: " . $adaptee->specificRequest();
echo "\n\n";
echo "Client: But I can work with it via the Adapter:\n";
$adapter = new Adapter($adaptee);
clientCode($adapter);
Output.txt: Resultados da execução
Client: I can work just fine with the Target objects:
Target: The default target's behavior.
Client: The Adaptee class has a weird interface. See, I don't understand it:
Adaptee: .eetpadA eht fo roivaheb laicepS
Client: But I can work with it via the Adapter:
Adapter: (TRANSLATED) Special behavior of the Adaptee.
Exemplo do mundo real
O padrão Adapter permite usar classes de terceiros ou herdadas, mesmo que sejam incompatíveis com a maior parte do seu código. Por exemplo, em vez de reescrever a interface de notificação do seu aplicativo para oferecer suporte a cada serviço de terceiros, como Slack, Facebook, SMS ou (você escolhe), você pode criar um conjunto de wrappers especiais que adaptam as chamadas do seu aplicativo para uma interface e formato exigidos por cada classe de terceiros.
index.php: Exemplo do mundo real
<?php
namespace RefactoringGuru\Adapter\RealWorld;
/**
* The Target interface represents the interface that your application's classes
* already follow.
*/
interface Notification
{
public function send(string $title, string $message);
}
/**
* Here's an example of the existing class that follows the Target interface.
*
* The truth is that many real apps may not have this interface clearly defined.
* If you're in that boat, your best bet would be to extend the Adapter from one
* of your application's existing classes. If that's awkward (for instance,
* SlackNotification doesn't feel like a subclass of EmailNotification), then
* extracting an interface should be your first step.
*/
class EmailNotification implements Notification
{
private $adminEmail;
public function __construct(string $adminEmail)
{
$this->adminEmail = $adminEmail;
}
public function send(string $title, string $message): void
{
mail($this->adminEmail, $title, $message);
echo "Sent email with title '$title' to '{$this->adminEmail}' that says '$message'.";
}
}
/**
* The Adaptee is some useful class, incompatible with the Target interface. You
* can't just go in and change the code of the class to follow the Target
* interface, since the code might be provided by a 3rd-party library.
*/
class SlackApi
{
private $login;
private $apiKey;
public function __construct(string $login, string $apiKey)
{
$this->login = $login;
$this->apiKey = $apiKey;
}
public function logIn(): void
{
// Send authentication request to Slack web service.
echo "Logged in to a slack account '{$this->login}'.\n";
}
public function sendMessage(string $chatId, string $message): void
{
// Send message post request to Slack web service.
echo "Posted following message into the '$chatId' chat: '$message'.\n";
}
}
/**
* The Adapter is a class that links the Target interface and the Adaptee class.
* In this case, it allows the application to send notifications using Slack
* API.
*/
class SlackNotification implements Notification
{
private $slack;
private $chatId;
public function __construct(SlackApi $slack, string $chatId)
{
$this->slack = $slack;
$this->chatId = $chatId;
}
/**
* An Adapter is not only capable of adapting interfaces, but it can also
* convert incoming data to the format required by the Adaptee.
*/
public function send(string $title, string $message): void
{
$slackMessage = "#" . $title . "# " . strip_tags($message);
$this->slack->logIn();
$this->slack->sendMessage($this->chatId, $slackMessage);
}
}
/**
* The client code can work with any class that follows the Target interface.
*/
function clientCode(Notification $notification)
{
// ...
echo $notification->send(
"Website is down!",
"<strong style='color:red;font-size: 50px;'>Alert!</strong> " .
"Our website is not responding. Call admins and bring it up!"
);
// ...
}
echo "Client code is designed correctly and works with email notifications:\n";
$notification = new EmailNotification("developers@example.com");
clientCode($notification);
echo "\n\n";
echo "The same client code can work with other classes via adapter:\n";
$slackApi = new SlackApi("example.com", "XXXXXXXX");
$notification = new SlackNotification($slackApi, "Example.com Developers");
clientCode($notification);
Output.txt: Resultados da execução
Client code is designed correctly and works with email notifications:
Sent email with title 'Website is down!' to 'developers@example.com' that says '<strong style='color:red;font-size: 50px;'>Alert!</strong> Our website is not responding. Call admins and bring it up!'.
The same client code can work with other classes via adapter:
Logged in to a slack account 'example.com'.
Posted following message into the 'Example.com Developers' chat: '#Website is down!# Alert! Our website is not responding. Call admins and bring it up!'.
