PHP面向对象程序设计之对象生成方法详解

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 formatn";
  }
}
class MegaApptEncoder extends ApptEncoder {
  function encode() {
    return "Appointment data encoded in MegaCal formatn";
  }
}
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 formatn";
  }
}
class MegaApptEncoder extends ApptEncoder {
  function encode() {
    return "Appointment data encoded in MegaCal formatn";
  }
}
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 headern";
      default:
        return "BloggsCal headern";
    }
  }
  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 formatn";
  }
}
class MegaApptEncoder extends ApptEncoder {
  function encode() {
    return "Appointment data encoded in MegaCal formatn";
  }
}
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 headern";
  }
  function getApptEncoder() {
    return new BloggsApptEncoder();
  }
  function getTtdEncoder() {
    return new BloggsTtdEncoder();
  }
  function getContactEncoder() {
    return new BloggsContactEncoder();
  }
  function getFooterText() {
    return "BloggsCal footern";
  }
}
class MegaCommsManager extends CommsManager {
  function getHeaderText() {
    return "MegaCal headern";
  }
  function getApptEncoder() {
    return new MegaApptEncoder();
  }
  function getTtdEncoder() {
    return new MegaTtdEncoder();
  }
  function getContactEncoder() {
    return new MegaContactEncoder();
  }
  function getFooterText() {
    return "MegaCal footern";
  }
}
$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();
?>

								 
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