设计模式系列 | 工厂方法模式

// 创建者类声明的工厂方法必须返回一个产品类的对象。创建者的子类通常会提供
// 该方法的实现。
class Dialog is
    // 创建者还可提供一些工厂方法的默认实现。
    abstract method createButton():Button

    // 请注意，创建者的主要职责并非是创建产品。其中通常会包含一些核心业务
    // 逻辑，这些逻辑依赖于由工厂方法返回的产品对象。子类可通过重写工厂方
    // 法并使其返回不同类型的产品来间接修改业务逻辑。
    method render() is
        // 调用工厂方法创建一个产品对象。
        Button okButton = createButton()
        // 现在使用产品。
        okButton.onClick(closeDialog)
        okButton.render()


// 具体创建者将重写工厂方法以改变其所返回的产品类型。
class WindowsDialog extends Dialog is
    method createButton():Button is
        return new WindowsButton()

class WebDialog extends Dialog is
    method createButton():Button is
        return new HTMLButton()


// 产品接口中将声明所有具体产品都必须实现的操作。
interface Button is
    method render()
    method onClick(f)

// 具体产品需提供产品接口的各种实现。
class WindowsButton implements Button is
    method render(a, b) is
        // 根据 Windows 样式渲染按钮。
    method onClick(f) is
        // 绑定本地操作系统点击事件。

class HTMLButton implements Button is
    method render(a, b) is
        // 返回一个按钮的 HTML 表述。
    method onClick(f) is
        // 绑定网络浏览器的点击事件。


class Application is
    field dialog: Dialog

    // 程序根据当前配置或环境设定选择创建者的类型。
    method initialize() is
        config = readApplicationConfigFile()

        if (config.OS == "Windows") then
            dialog = new WindowsDialog()
        else if (config.OS == "Web") then
            dialog = new WebDialog()
        else
            throw new Exception("错误！未知的操作系统。")

    // 当前客户端代码会与具体创建者的实例进行交互，但是必须通过其基本接口
    // 进行。只要客户端通过基本接口与创建者进行交互，你就可将任何创建者子
    // 类传递给客户端。
    method main() is
        this.initialize()
        dialog.render()

<?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", "******"));

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