PHP中的实现Registry模式过程中的领悟

<?php
/*
Singleton && Registry Design Pattern Implementation
*/
class Registry {
private $_store = array();
public function getInstance() {
static $instance = array();
if (!$instance) {
$instance[0] = new Registry;
}
return $instance[0];
}
public function &get($key){
if($this->isValid($key)){
return $this->_store[$key];
}
}
public function set($key, $object){
$this->_store[$key] = &$object;
}
public function isValid($key){
return array_key_exists($key,$this->_store);
}
}
?>
Test Case:
<?php
require_once 'simpletest/unit_tester.php';
require_once 'simpletest/reporter.php';
require_once 'Registry.php';
class RegistryTestCase extends UnitTestCase{
function testRegistryIsSingleton(){
$this->assertIsA($reg = Registry::getInstance(), 'Registry');
$this->assertReference($reg, Registry::getInstance());
}
function testEmptyRegistryKeyIsReturnNull(){
$reg = Registry::getInstance();
$this->assertNull($reg->get('key'));
}
function testEmptyRegistryKeyIsInvalid(){
$reg = Registry::getInstance();
$this->assertFalse($reg->get('key'));
}
function testSetRegistryKeyBecomesValid(){
$reg = Registry::getInstance();
$test_value = 'something';
settype($test_value, 'Object');
$reg->set('key', $test_value);
$this->assertTrue($reg->isValid('key'));
}
function testRegistryValueIsReference(){
$reg = Registry::getInstance();
$test_value = 'something';
$reg->set('key', $test_value);