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PHP 工厂方法模式讲解和代码示例

工厂方法是一种创建型设计模式， 解决了在不指定具体类的情况下创建产品对象的问题。

工厂方法定义了一个方法， 且必须使用该方法代替通过直接调用构造函数来创建对象 （ new操作符） 的方式。 子类可重写该方法来更改将被创建的对象所属类。

如果你不清楚工厂、 工厂方法和抽象工厂模式之间的区别， 请参阅工厂模式比较。

** 进一步了解工厂方法模式 **

复杂度：******

流行度：******

使用示例： 工厂方法模式在 PHP 代码中得到了广泛使用。 当你需要在代码中提供高层次的灵活性时， 该模式会非常实用。

识别方法： 工厂方法可通过构建方法来识别， 它会创建具体类的对象， 但以抽象类型或接口的形式返回这些对象。

概念示例真实世界示例

真实世界示例

在本例中， 工厂方法模式为创建社交网络连接器提供接口， 可用于进行登录网络、 发帖和潜在的其他行为， 而实现所有这些功能都无需客户端代码与特定社交网络的特定类相耦合。

** index.php:  真实世界示例

<?php

namespace RefactoringGuru\FactoryMethod\RealWorld;

/**
 * The Creator declares a factory method that can be used as a substitution for
 * the direct constructor calls of products, for instance:
 *
 * - Before: $p = new FacebookConnector();
 * - After: $p = $this->getSocialNetwork;
 *
 * This allows changing the type of the product being created by
 * SocialNetworkPoster's subclasses.
 */
abstract class SocialNetworkPoster
{
    /**
     * The actual factory method. Note that it returns the abstract connector.
     * This lets subclasses return any concrete connectors without breaking the
     * superclass' contract.
     */
    abstract public function getSocialNetwork(): SocialNetworkConnector;

    /**
     * When the factory method is used inside the Creator's business logic, the
     * subclasses may alter the logic indirectly by returning different types of
     * the connector from the factory method.
     */
    public function post($content): void
    {
        // Call the factory method to create a Product object...
        $network = $this->getSocialNetwork();
        // ...then use it as you will.
        $network->logIn();
        $network->createPost($content);
        $network->logout();
    }
}

/**
 * This Concrete Creator supports Facebook. Remember that this class also
 * inherits the 'post' method from the parent class. Concrete Creators are the
 * classes that the Client actually uses.
 */
class FacebookPoster extends SocialNetworkPoster
{
    private $login, $password;

    public function __construct(string $login, string $password)
    {
        $this->login = $login;
        $this->password = $password;
    }

    public function getSocialNetwork(): SocialNetworkConnector
    {
        return new FacebookConnector($this->login, $this->password);
    }
}

/**
 * This Concrete Creator supports LinkedIn.
 */
class LinkedInPoster extends SocialNetworkPoster
{
    private $email, $password;

    public function __construct(string $email, string $password)
    {
        $this->email = $email;
        $this->password = $password;
    }

    public function getSocialNetwork(): SocialNetworkConnector
    {
        return new LinkedInConnector($this->email, $this->password);
    }
}

/**
 * The Product interface declares behaviors of various types of products.
 */
interface SocialNetworkConnector
{
    public function logIn(): void;

    public function logOut(): void;

    public function createPost($content): void;
}

/**
 * This Concrete Product implements the Facebook API.
 */
class FacebookConnector implements SocialNetworkConnector
{
    private $login, $password;

    public function __construct(string $login, string $password)
    {
        $this->login = $login;
        $this->password = $password;
    }

    public function logIn(): void
    {
        echo "Send HTTP API request to log in user $this->login with " .
            "password $this->password\n";
    }

    public function logOut(): void
    {
        echo "Send HTTP API request to log out user $this->login\n";
    }

    public function createPost($content): void
    {
        echo "Send HTTP API requests to create a post in Facebook timeline.\n";
    }
}

/**
 * This Concrete Product implements the LinkedIn API.
 */
class LinkedInConnector implements SocialNetworkConnector
{
    private $email, $password;

    public function __construct(string $email, string $password)
    {
        $this->email = $email;
        $this->password = $password;
    }

    public function logIn(): void
    {
        echo "Send HTTP API request to log in user $this->email with " .
            "password $this->password\n";
    }

    public function logOut(): void
    {
        echo "Send HTTP API request to log out user $this->email\n";
    }

    public function createPost($content): void
    {
        echo "Send HTTP API requests to create a post in LinkedIn timeline.\n";
    }
}

/**
 * The client code can work with any subclass of SocialNetworkPoster since it
 * doesn't depend on concrete classes.
 */
function clientCode(SocialNetworkPoster $creator)
{
    // ...
    $creator->post("Hello world!");
    $creator->post("I had a large hamburger this morning!");
    // ...
}

/**
 * During the initialization phase, the app can decide which social network it
 * wants to work with, create an object of the proper subclass, and pass it to
 * the client code.
 */
echo "Testing ConcreteCreator1:\n";
clientCode(new FacebookPoster("john_smith", "******"));
echo "\n\n";

echo "Testing ConcreteCreator2:\n";
clientCode(new LinkedInPoster("john_smith@example.com", "******"));

** Output.txt:  执行结果

Testing ConcreteCreator1:
Send HTTP API request to log in user john_smith with password ******
Send HTTP API requests to create a post in Facebook timeline.
Send HTTP API request to log out user john_smith
Send HTTP API request to log in user john_smith with password ******
Send HTTP API requests to create a post in Facebook timeline.
Send HTTP API request to log out user john_smith


Testing ConcreteCreator2:
Send HTTP API request to log in user john_smith@example.com with password ******
Send HTTP API requests to create a post in LinkedIn timeline.
Send HTTP API request to log out user john_smith@example.com
Send HTTP API request to log in user john_smith@example.com with password ******
Send HTTP API requests to create a post in LinkedIn timeline.
Send HTTP API request to log out user john_smith@example.com