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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