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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