PHP面向对象程序设计之对象生成方法详解

本文实例讲述了PHP面向对象程序设计之对象生成方法。分享给大家供大家参考，具体如下：

对象

看个例子

    <?php
    abstract class Employee { // 雇员
      protected $name;
      function __construct( $name ) {
        $this->name = $name;
      }
      abstract function fire();
    }
    class Minion extends Employee { // 奴隶 继承 雇员
      function fire() {
        print "{$this->name}: I'll clear my desk\n";
      }
    }
    class NastyBoss { // 坏老板
      private $employees = array();
      function addEmployee( $employeeName ) { // 添加员工
        $this->employees[] = new Minion( $employeeName ); // 代码灵活性受到限制
      }
      function projectFails() {
        if ( count( $this->employees ) > 0 ) {
          $emp = array_pop( $this->employees );
          $emp->fire(); // 炒鱿鱼
        }
      }
    }
    $boss = new NastyBoss();
    $boss->addEmployee( "harry" );
    $boss->addEmployee( "bob" );
    $boss->addEmployee( "mary" );
    $boss->projectFails();
    // output:
    // mary: I'll clear my desk
    ?>

再看一个更具有灵活性的案例

    <?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\n";
      }
    }
    class NastyBoss {
      private $employees = array(); 
      function addEmployee( Employee $employee ) { // 传入对象
        $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\n";
      }
    }
    $boss = new NastyBoss();
    $boss->addEmployee( new Minion( "harry" ) ); // 直接以对象作为参数，更具有灵活性
    $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
    ?>

单例

    <?php
    class Preferences {
      private $props = array();
      private static $instance; // 私有的，静态属性
      private function __construct() { } // 无法实例化，私有的构造函数
      public static function getInstance() { // 返回对象 静态方法才可以被类访问，静态方法中要有静态属性
        if ( empty( self::$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" ) ."\n"; // demonstrate value is not lost
    ?>

点评：不能随意创建对象，只能通过Preferences::getInstance()来创建对象。

工厂模式

    <?php
    abstract class ApptEncoder {
      abstract function encode();
    }
    class BloggsApptEncoder extends ApptEncoder {
      function encode() {
        return "Appointment data encoded in BloggsCal format\n";
      }
    }
    class MegaApptEncoder extends ApptEncoder {
      function encode() {
        return "Appointment data encoded in MegaCal format\n";
      }
    }
    class CommsManager { // 负责生产Bloggs对象
      function getApptEncoder() {
        return new BloggsApptEncoder();
      }
    }
    $obj = new CommsManager();
    $bloggs = $obj->getApptEncoder(); // 获取对象
    print $bloggs->encode();
    ?>

output:

Appointment data encoded in BloggsCal format

进一步增加灵活性设置

    <?php
    abstract class ApptEncoder {
      abstract function encode();
    }
    class BloggsApptEncoder extends ApptEncoder {
      function encode() {
        return "Appointment data encoded in BloggsCal format\n";
      }
    }
    class MegaApptEncoder extends ApptEncoder {
      function encode() {
        return "Appointment data encoded in MegaCal format\n";
      }
    }
    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\n";
          default:
            return "BloggsCal header\n";
        }
      }
      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() ) )."\n";
    $man = new CommsManager( CommsManager::BLOGGS );
    print ( get_class( $man->getApptEncoder() ) )."\n";
    ?>

output:

MegaApptEncoder
BloggsApptEncoder

工厂方法模式要把创建者类与要生产的产品类分离开来。

抽象工厂

通过抽象来来约束，成为一定的规矩。

    <?php
    abstract class ApptEncoder {
      abstract function encode();
    }
    class BloggsApptEncoder extends ApptEncoder {
      function encode() {
        return "Appointment data encoded in BloggsCal format\n";
      }
    }
    class MegaApptEncoder extends ApptEncoder {
      function encode() {
        return "Appointment data encoded in MegaCal format\n";
      }
    }
    abstract class CommsManager { // 预约
      abstract function getHeaderText();
      abstract function getApptEncoder();
      abstract function getTtdEncoder();
      abstract function getContactEncoder();
      abstract function getFooterText();
    }
    class BloggsCommsManager extends CommsManager {
      function getHeaderText() {
        return "BloggsCal header\n";
      }
      function getApptEncoder() {
        return new BloggsApptEncoder();
      }
      function getTtdEncoder() {
        return new BloggsTtdEncoder();
      }
      function getContactEncoder() {
        return new BloggsContactEncoder();
      }
      function getFooterText() {
        return "BloggsCal footer\n";
      }
    }
    class MegaCommsManager extends CommsManager {
      function getHeaderText() {
        return "MegaCal header\n";
      }
      function getApptEncoder() {
        return new MegaApptEncoder();
      }
      function getTtdEncoder() {
        return new MegaTtdEncoder();
      }
      function getContactEncoder() {
        return new MegaContactEncoder();
      }
      function getFooterText() {
        return "MegaCal footer\n";
      }
    }
    $mgr = new MegaCommsManager();
    print $mgr->getHeaderText();
    print $mgr->getApptEncoder()->encode(); // 对象调用方法，返回对象，继续调用方法。
    print $mgr->getFooterText();
    ?>

output:

MegaCal header
Appointment data encoded in MegaCal format
MegaCal footer

更加牛逼的实现

    <?php
    // 根据类图，规划类的代码。从大局入手。
    abstract class ApptEncoder {
      abstract function encode();
    }
    class BloggsApptEncoder extends ApptEncoder {
      function encode() {
        return "Appointment data encoded in BloggsCal format\n";
      }
    }
    class MegaApptEncoder extends ApptEncoder {
      function encode() {
        return "Appointment data encoded in MegaCal format\n";
      }
    }
    abstract class CommsManager {
      const APPT  = 1;
      const TTD   = 2;
      const CONTACT = 3;
      abstract function getHeaderText();
      abstract function make( $flag_int ); // int标记
      abstract function getFooterText();
    }
    class BloggsCommsManager extends CommsManager {
      function getHeaderText() {
        return "BloggsCal header\n";
      }
      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\n";
      }
    }
    $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

改造成一个保存具体产品的工厂类。

    <?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 { // 地域工厂
      private $sea;
      private $forest;
      private $plains;
      function __construct( Sea $sea, Plains $plains, Forest $forest ) { // 定义变量为类对象
        $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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希望本文所述对大家PHP程序设计有所帮助。