<?php

class SomeComponent
{
    /**
     * 连接数据库的实例是被写死在组件的内部
     * 因此，我们很难从外部替换或者改变它的行为
     */
    public function someDbTask()
    {
        $connection = new Connection(
            array(
                "host"     => "localhost",
                "username" => "root",
                "password" => "secret",
                "dbname"   => "invo"
            )
        );

        // ...
    }
}

$some = new SomeComponent();
$some->someDbTask();

<?php

class SomeComponent
{
    protected $_connection;

    /**
     * 设置外部传入的数据库的连接实例
     */
    public function setConnection($connection)
    {
        $this->_connection = $connection;
    }

    public function someDbTask()
    {
        $connection = $this->_connection;

        // ...
    }
}

$some = new SomeComponent();

// 建立数据库连接实例
$connection = new Connection(
    array(
        "host"     => "localhost",
        "username" => "root",
        "password" => "secret",
        "dbname"   => "invo"
    )
);

// 向组件注入数据连接实例
$some->setConnection($connection);

$some->someDbTask();

<?php

class Registry
{
    /**
     * 返回数据库连接实例
     */
    public static function getConnection()
    {
        return new Connection(
            array(
                "host"     => "localhost",
                "username" => "root",
                "password" => "secret",
                "dbname"   => "invo"
            )
        );
    }
}

class SomeComponent
{
    protected $_connection;

    /**
     * 设置外部传入的数据库的连接实例
     */
    public function setConnection($connection)
    {
        $this->_connection = $connection;
    }

    public function someDbTask()
    {
        $connection = $this->_connection;

        // ...
    }
}

$some = new SomeComponent();

// 把注册表中的连接实例传递给组件
$some->setConnection(Registry::getConnection());

$some->someDbTask();

<?php

class Registry
{
    protected static $_connection;

    /**
     * 建立一个新的连接实例
     */
    protected static function _createConnection()
    {
        return new Connection(
            array(
                "host"     => "localhost",
                "username" => "root",
                "password" => "secret",
                "dbname"   => "invo"
            )
        );
    }

    /**
     * 只建立一个连接实例，后面的请求只返回该连接实例
     */
    public static function getSharedConnection()
    {
        if (self::$_connection===null) {
            $connection = self::_createConnection();
            self::$_connection = $connection;
        }

        return self::$_connection;
    }

    /**
     * 总是返回一个新的连接实例
     */
    public static function getNewConnection()
    {
        return self::_createConnection();
    }
}

class SomeComponent
{
    protected $_connection;

    /**
     * 设置外部传入的数据库的连接实例
     */
    public function setConnection($connection)
    {
        $this->_connection = $connection;
    }

    /**
     * 这个方法总是需要共享连接实例
     */
    public function someDbTask()
    {
        $connection = $this->_connection;

        // ...
    }

    /**
     * 这个方法总是需要新的连接实例
     */
    public function someOtherDbTask($connection)
    {

    }
}

$some = new SomeComponent();

// 注入共享连接实例
$some->setConnection(Registry::getSharedConnection());

$some->someDbTask();

// 这里我们总是传递一个新的连接实例
$some->someOtherDbTask(Registry::getConnection());

<?php

// 创建依赖实例或从注册表中查找
$connection = new Connection();
$session    = new Session();
$fileSystem = new FileSystem();
$filter     = new Filter();
$selector   = new Selector();

// 把实例作为参数传递给构造函数
$some = new SomeComponent($connection, $session, $fileSystem, $filter, $selector);

// ... 或者使用setter

$some->setConnection($connection);
$some->setSession($session);
$some->setFileSystem($fileSystem);
$some->setFilter($filter);
$some->setSelector($selector);

<?php

class SomeComponent
{
    // ...

    /**
     * Define a factory method to create SomeComponent instances injecting its dependencies
     */
    public static function factory()
    {
        $connection = new Connection();
        $session    = new Session();
        $fileSystem = new FileSystem();
        $filter     = new Filter();
        $selector   = new Selector();

        return new self($connection, $session, $fileSystem, $filter, $selector);
    }
}

<?php

use PhalconDI;

class SomeComponent
{
    protected $_di;

    public function __construct($di)
    {
        $this->_di = $di;
    }

    public function someDbTask()
    {
        // 获得数据库连接实例
        // 总是返回一个新的连接
        $connection = $this->_di->get('db');
    }

    public function someOtherDbTask()
    {
        // 获得共享连接实例
        // 每次请求都返回相同的连接实例
        $connection = $this->_di->getShared('db');

        // 这个方法也需要一个输入过滤的依赖服务
        $filter = $this->_di->get('filter');
    }
}

$di = new DI();

// 在容器中注册一个db服务
$di->set('db', function () {
    return new Connection(
        array(
            "host"     => "localhost",
            "username" => "root",
            "password" => "secret",
            "dbname"   => "invo"
        )
    );
});

// 在容器中注册一个filter服务
$di->set('filter', function () {
    return new Filter();
});

// 在容器中注册一个session服务
$di->set('session', function () {
    return new Session();
});

// 把传递服务的容器作为唯一参数传递给组件
$some = new SomeComponent($di);

$some->someDbTask();