?* 虛代理,只有在被拜訪成員時才調用閉包函數生成目標對象.
?*
?* @author tonyseek
?*
?*/
class VirtualProxy
{
??? private $holder = null;
??? private $loader = null;

??? /**
???? * 虛代理,只有在被拜訪成員時才調用閉包函數生成目標對象.
???? *
???? * @param Closure $loader 生成被代理對象的閉包函數
???? */
??? public function __construct(Closure $loader)
??? {
??????????? $this->loader = $loader;
??? }PHP編程

??? /**
???? * 代理成員方法的調用
???? *
???? * @param string $method
???? * @param array? $arguments
???? * @throws BadMethodCallException
???? * @return mixed
???? */
??? public function __call($method, array $arguments = null)
??? {
??????????? $this->check();PHP編程

??????????? if (!method_exists($this->holder, $method)) {
??????????????????? throw new BadMethodCallException();
??????????? }PHP編程

??????????? return call_user_func_array(
??????????????????? array(&$this->holder, $method),
??????????????????? $arguments);
??? }PHP編程

??? /**
???? * 代理成員屬性的讀取
???? *
???? * @param string $property
???? * @throws ErrorException
???? * @return mixed
???? */
??? public function __get($property)
??? {
??????????? $this->check();PHP編程

??????????? if (!isset($this->holder->$property)) {
??????????????????? throw new ErrorException();
??????????? }PHP編程

??????????? return $this->holder->$property;
??? }PHP編程

??? /**
???? * 代理成員屬性的賦值
???? *
???? * @param string $property
???? * @param mixed? $value
???? */
??? public function __set($property, $value)
??? {
??????????? $this->check();PHP編程

??????????? $this->holder->$property = $value;
??? }PHP編程

??? /**
???? * 檢查是否已經存在被代理對象,不存在則生成.
???? */
??? private function check()
??? {
??????????? if (null == $this->holder) {
??????????????????? $loader = $this->loader;
??????????????????? $this->holder = $loader();
??????????? }
??? }
}PHP編程

// 測試
$v = new VirtualProxy(function(){
??????? echo 'Now, Loading', "\n";
??? $a = new ArrayObject(range(1,100));
??? $a->abc = 'a';
??????? // 實際使用中,這里調用的是 DataMapper 的 findXXX 方法
??????? // 返回的是領域對象集合
??? return $a;
});
// 代理對象直接當作原對象拜訪
// 而此時構造方法傳入的 callback 函數才被調用
// 從而實現加載對象操作的延遲
echo $v->abc . $v->offsetGet(50);
PHP編程