PHP物件導向深入研究之【物件生成】

桃子紅了吶發表於2016-11-27

物件

看個例子

<?php
abstract class Employee { // 僱員
    protected $name;
    function __construct( $name ) {
        $this->name = $name;
    }
    abstract function fire();
}

class Minion extends Employee { // 奴隸 繼承 僱員
    function fire() {
        print "{$this->name}: I`ll clear my desk
";
    }
}

class NastyBoss { // 壞老闆
    private $employees = array();

    function addEmployee( $employeeName ) { // 新增員工
        $this->employees[] = new Minion( $employeeName ); // 程式碼靈活性受到限制
    }

    function projectFails() {
        if ( count( $this->employees ) > 0 ) {
            $emp = array_pop( $this->employees );
            $emp->fire(); // 炒魷魚
        }
    }
}

$boss = new NastyBoss();
$boss->addEmployee( "harry" );
$boss->addEmployee( "bob" );
$boss->addEmployee( "mary" );
$boss->projectFails();

// output:
// mary: I`ll clear my desk
?>

再看一個更具有靈活性的案例

<?php

abstract class Employee {
    protected $name;
    function __construct( $name ) {
        $this->name = $name;
    }
    abstract function fire();
}

class Minion extends Employee {
    function fire() {
        print "{$this->name}: I`ll clear my desk
";
    }
}

class NastyBoss {
    private $employees = array(); 

    function addEmployee( Employee $employee ) { // 傳入物件
        $this->employees[] = $employee;
    }

    function projectFails() {
        if ( count( $this->employees ) ) {
            $emp = array_pop( $this->employees );
            $emp->fire();
        }
    }
}

// new Employee class...
class CluedUp extends Employee {
    function fire() {
        print "{$this->name}: I`ll call my lawyer
";
    }
}

$boss = new NastyBoss();
$boss->addEmployee( new Minion( "harry" ) ); // 直接以物件作為引數，更具有靈活性
$boss->addEmployee( new CluedUp( "bob" ) );
$boss->addEmployee( new Minion( "mary" ) );
$boss->projectFails();
$boss->projectFails();
$boss->projectFails();
// output:
// mary: I`ll clear my desk
// bob: I`ll call my lawyer
// harry: I`ll clear my desk
?>

單例

<?php

class Preferences {
    private $props = array();
    private static $instance; // 私有的，靜態屬性

    private function __construct() { } // 無法例項化，私有的建構函式

    public static function getInstance() { // 返回物件 靜態方法才可以被類訪問，靜態方法中要有靜態屬性
        if ( empty( self::$instance ) ) {
            self::$instance = new Preferences();
        }
        return self::$instance;
    }

    public function setProperty( $key, $val ) {
        $this->props[$key] = $val;
    }

    public function getProperty( $key ) {
        return $this->props[$key];
    }
}


$pref = Preferences::getInstance();
$pref->setProperty( "name", "matt" );

unset( $pref ); // remove the reference

$pref2 = Preferences::getInstance();
print $pref2->getProperty( "name" ) ."
"; // demonstrate value is not lost
?>

點評：不能隨意建立物件，只能通過Preferences::getInstance()來建立物件。

工廠模式

<?php

abstract class ApptEncoder {
    abstract function encode();
}

class BloggsApptEncoder extends ApptEncoder {
    function encode() {
        return "Appointment data encoded in BloggsCal format
";
    }
}

class MegaApptEncoder extends ApptEncoder {
    function encode() {
        return "Appointment data encoded in MegaCal format
";
    }
}

class CommsManager { // 負責生產Bloggs物件
    function getApptEncoder() {
        return new BloggsApptEncoder();
    }
}

$obj = new CommsManager();
$bloggs = $obj->getApptEncoder(); // 獲取物件
print $bloggs->encode();
?>
output:
Appointment data encoded in BloggsCal format

進一步增加靈活性設定

<?php

abstract class ApptEncoder {
    abstract function encode();
}

class BloggsApptEncoder extends ApptEncoder {
    function encode() {
        return "Appointment data encoded in BloggsCal format
";
    }
}

class MegaApptEncoder extends ApptEncoder {
    function encode() {
        return "Appointment data encoded in MegaCal format
";
    }
}

class CommsManager {
    const BLOGGS = 1;
    const MEGA = 2;
    private $mode ;

    function __construct( $mode ) {
        $this->mode = $mode;
    }

    function getHeaderText() {
        switch ( $this->mode ) {
            case ( self::MEGA ):
                return "MegaCal header
";
            default:
                return "BloggsCal header
";
        }
    }
    function getApptEncoder() {
        switch ( $this->mode ) {
            case ( self::MEGA ):
                return new MegaApptEncoder();
            default:
                return new BloggsApptEncoder();
        }
    }
}

$man = new CommsManager( CommsManager::MEGA );
print ( get_class( $man->getApptEncoder() ) )."
";
$man = new CommsManager( CommsManager::BLOGGS );
print ( get_class( $man->getApptEncoder() ) )."
";
?>
output:
MegaApptEncoder
BloggsApptEncoder

工廠方法模式要把建立者類與要生產的產品類分離開來。

抽象工廠

通過抽象來來約束，成為一定的規矩。

<?php
abstract class ApptEncoder {
    abstract function encode();
}

class BloggsApptEncoder extends ApptEncoder {
    function encode() {
        return "Appointment data encoded in BloggsCal format
";
    }
}

class MegaApptEncoder extends ApptEncoder {
    function encode() {
        return "Appointment data encoded in MegaCal format
";
    }
}


abstract class CommsManager { // 預約
    abstract function getHeaderText();
    abstract function getApptEncoder();
    abstract function getTtdEncoder();
    abstract function getContactEncoder();
    abstract function getFooterText();
}

class BloggsCommsManager extends CommsManager {
    function getHeaderText() {
        return "BloggsCal header
";
    }

    function getApptEncoder() {
        return new BloggsApptEncoder();
    }

    function getTtdEncoder() {
        return new BloggsTtdEncoder();
    }

    function getContactEncoder() {
        return new BloggsContactEncoder();
    }

    function getFooterText() {
        return "BloggsCal footer
";
    }
}

class MegaCommsManager extends CommsManager {
    function getHeaderText() {
        return "MegaCal header
";
    }

    function getApptEncoder() {
        return new MegaApptEncoder();
    }

    function getTtdEncoder() {
        return new MegaTtdEncoder();
    }

    function getContactEncoder() {
        return new MegaContactEncoder();
    }

    function getFooterText() {
        return "MegaCal footer
";
    }
}


$mgr = new MegaCommsManager();
print $mgr->getHeaderText();
print $mgr->getApptEncoder()->encode(); // 物件呼叫方法，返回物件，繼續呼叫方法。
print $mgr->getFooterText();

?>
output:
MegaCal header
Appointment data encoded in MegaCal format
MegaCal footer

更加牛逼的實現

<?php
// 根據類圖，規劃類的程式碼。從大局入手。
abstract class ApptEncoder {
    abstract function encode();
}

class BloggsApptEncoder extends ApptEncoder {
    function encode() {
        return "Appointment data encoded in BloggsCal format
";
    }
}

class MegaApptEncoder extends ApptEncoder {
    function encode() {
        return "Appointment data encoded in MegaCal format
";
    }
}

abstract class CommsManager {
    const APPT    = 1;
    const TTD     = 2;
    const CONTACT = 3;
    abstract function getHeaderText();
    abstract function make( $flag_int ); // int標記
    abstract function getFooterText();
}

class BloggsCommsManager extends CommsManager {
    function getHeaderText() {
        return "BloggsCal header
";
    }
    function make( $flag_int ) {
        switch ( $flag_int ) {
            case self::APPT: // self直接控制常量
                return new BloggsApptEncoder();
            case self::CONTACT:
                return new BloggsContactEncoder();
            case self::TTD:
                return new BloggsTtdEncoder();
        }
    }

    function getFooterText() {
        return "BloggsCal footer
";
    }
}

$mgr = new BloggsCommsManager();
print $mgr->getHeaderText();
print $mgr->make( CommsManager::APPT )->encode();
print $mgr->getFooterText();


?>
output:
BloggsCal header
Appointment data encoded in BloggsCal format
BloggsCal footer

原型模式

改造成一個儲存具體產品的工廠類。

<?php

class Sea {} // 大海
class EarthSea extends Sea {}
class MarsSea extends Sea {}

class Plains {} // 平原
class EarthPlains extends Plains {}
class MarsPlains extends Plains {}

class Forest {} // 森林
class EarthForest extends Forest {}
class MarsForest extends Forest {}

class TerrainFactory { // 地域工廠
    private $sea;
    private $forest;
    private $plains;

    function __construct( Sea $sea, Plains $plains, Forest $forest ) { // 定義變數為類物件
        $this->sea = $sea;
        $this->plains = $plains;
        $this->forest = $forest;
    }

    function getSea( ) {
        return clone $this->sea; // 克隆
    }

    function getPlains( ) {
        return clone $this->plains;
    }

    function getForest( ) {
        return clone $this->forest;
    }
}

$factory = new TerrainFactory( new EarthSea(),
    new EarthPlains(),
    new EarthForest() );
print_r( $factory->getSea() );
print_r( $factory->getPlains() );
print_r( $factory->getForest() );
?>
output:
EarthSea Object
(
)
EarthPlains Object
(
)
EarthForest Object
(
)

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PHP物件導向深入研究之【物件生成】

物件

單例

工廠模式

抽象工廠

原型模式

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