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PHP 模板方法模式讲解和代码示例

模版方法是一种行为设计模式， 它在基类中定义了一个算法的框架， 允许子类在不修改结构的情况下重写算法的特定步骤。

** 进一步了解模板方法模式 **

复杂度：******

流行度：******

使用示例： 模版方法模式在 PHP 框架中很常见。 该模式简化了通过类继承对默认框架行为进行扩展时的工作。

识别方法： 模版方法可以通过行为方法来识别， 该方法已有一个在基类中定义的 “默认” 行为。

概念示例真实世界示例

真实世界示例

在本例中， 模版方法模式定义了在社交网络上发布消息的算法框架。 每个子类都代表一个不同的社交网络， 它们虽以不同方式实现所有步骤， 但却会复用基本的算法。

** index.php:  真实世界示例

<?php

namespace RefactoringGuru\TemplateMethod\RealWorld;

/**
 * The Abstract Class defines the template method and declares all its steps.
 */
abstract class SocialNetwork
{
    protected $username;

    protected $password;

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

    /**
     * The actual template method calls abstract steps in a specific order. A
     * subclass may implement all of the steps, allowing this method to actually
     * post something to a social network.
     */
    public function post(string $message): bool
    {
        // Authenticate before posting. Every network uses a different
        // authentication method.
        if ($this->logIn($this->username, $this->password)) {
            // Send the post data. All networks have different APIs.
            $result = $this->sendData($message);
            // ...
            $this->logOut();

            return $result;
        }

        return false;
    }

    /**
     * The steps are declared abstract to force the subclasses to implement them
     * all.
     */
    abstract public function logIn(string $userName, string $password): bool;

    abstract public function sendData(string $message): bool;

    abstract public function logOut(): void;
}

/**
 * This Concrete Class implements the Facebook API (all right, it pretends to).
 */
class Facebook extends SocialNetwork
{
    public function logIn(string $userName, string $password): bool
    {
        echo "\nChecking user's credentials...\n";
        echo "Name: " . $this->username . "\n";
        echo "Password: " . str_repeat("*", strlen($this->password)) . "\n";

        simulateNetworkLatency();

        echo "\n\nFacebook: '" . $this->username . "' has logged in successfully.\n";

        return true;
    }

    public function sendData(string $message): bool
    {
        echo "Facebook: '" . $this->username . "' has posted '" . $message . "'.\n";

        return true;
    }

    public function logOut(): void
    {
        echo "Facebook: '" . $this->username . "' has been logged out.\n";
    }
}

/**
 * This Concrete Class implements the Twitter API.
 */
class Twitter extends SocialNetwork
{
    public function logIn(string $userName, string $password): bool
    {
        echo "\nChecking user's credentials...\n";
        echo "Name: " . $this->username . "\n";
        echo "Password: " . str_repeat("*", strlen($this->password)) . "\n";

        simulateNetworkLatency();

        echo "\n\nTwitter: '" . $this->username . "' has logged in successfully.\n";

        return true;
    }

    public function sendData(string $message): bool
    {
        echo "Twitter: '" . $this->username . "' has posted '" . $message . "'.\n";

        return true;
    }

    public function logOut(): void
    {
        echo "Twitter: '" . $this->username . "' has been logged out.\n";
    }
}

/**
 * A little helper function that makes waiting times feel real.
 */
function simulateNetworkLatency()
{
    $i = 0;
    while ($i < 5) {
        echo ".";
        sleep(1);
        $i++;
    }
}

/**
 * The client code.
 */
echo "Username: \n";
$username = readline();
echo "Password: \n";
$password = readline();
echo "Message: \n";
$message = readline();

echo "\nChoose the social network to post the message:\n" .
    "1 - Facebook\n" .
    "2 - Twitter\n";
$choice = readline();

// Now, let's create a proper social network object and send the message.
if ($choice == 1) {
    $network = new Facebook($username, $password);
} elseif ($choice == 2) {
    $network = new Twitter($username, $password);
} else {
    die("Sorry, I'm not sure what you mean by that.\n");
}
$network->post($message);

** Output.txt:  执行结果

Username:
> neo
Password:
> 123123
Message:
> What is the Matrix?

Choose the social network to post the message:
1 - Facebook
2 - Twitter
> 1

Checking user's credentials...
Name: neo
Password: ******
.....

Facebook: 'neo' has logged in successfully.
Facebook: 'neo' has posted 'What is the Matrix?'.
Facebook: 'neo' has been logged out.