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復制代碼 代碼如下:
class Collection{
private $_members=array();
public function addItem($obj,$key=null)
{
if($key)
{
if(isset($this->_members[$key]))
{
throw new exception("Key /"$key/" already in use!");
}
else
{
$this->_members[$key]=$obj;
}
}
else
{
$this->_members[]=$obj;
}
}
public function removeItem($key)
{
if(isset($this->_members[$key]))
{
unset($this->_members[$key]);
}
else
{
throw new exception("Invalid Key /"$key/"!");
}
}
public function getItem($key)
{
if(isset($this->_members[$key]))
{
return $this->_members[$key];
}
else
{
throw new exception("Invalid Key /"$key/"!");
}
}
public function Keys()
{
return array_keys($this->_members);
}
public function legth()
{
return sizeof($this->_members);
}
public function exists($key)
{
return (isset($this->_members[$key]));
}
}
現在我們來測試一下這個集合是否好用。
我們首先建立一個集合元素類Course：
復制代碼 代碼如下:
class Course
{
private $_id;
private $_courseCode;
private $_name;
public function __construct($id,$courseCode,$name)
{
$this->_id=$id;
$this->_courseCode=$courseCode;
$this->_name=$name;
}
public function getName()
{
return $this->_name;
}
public function getID()
{
return $this->_id;
}
public function getCourseCode()
{
return $this->_courseCode;
}
public function __toString()
{
return $this->_name;
}
}
測試代碼如下：
$courses=new Collection();
$courses->addItem(new Course(1, "001", "語文"),1);
$courses->addItem(new Course(2, "002", "數學"),2);
$obj=$courses->getItem(1);
print $obj;
我想這個集合類應該可以滿足我們平日開發的需求了吧。
可是我們現在。NET里面有個對象延遲加載，舉個例子來說吧，假如現在有Student這個對象，它應該有很多Course，但是我們希望在訪問Course之前Course是不會加載的。也就是說在實例化Student的時候Course個數為0，當我們需要Course的時候它才真正從數據庫讀取相應數據。就是需要我們把Collection做成惰性實例化。
修改后的Collection代碼如下：
復制代碼 代碼如下:
class Collection {
private $_members = array(); //collection members
private $_onload; //holder for callback function
private $_isLoaded = false; //flag that indicates whether the callback
//has been invoked
public function addItem($obj, $key = null) {
$this->_checkCallback(); //_checkCallback is defined a little later
if($key) {
if(isset($this->_members[$key])) {
throw new KeyInUseException("Key /"$key/" already in use!");
} else {
$this->_members[$key] = $obj;
}
} else {
$this->_members[] = $obj;
}
}
public function removeItem($key) {
$this->_checkCallback();
if(isset($this->_members[$key])) {
unset($this->_members[$key]);
} else {
throw new KeyInvalidException("Invalid key /"$key/"!");
}
}
public function getItem($key) {
$this->_checkCallback();
if(isset($this->_members[$key])) {
return $this->_members[$key];
} else {
throw new KeyInvalidException("Invalid key /"$key/"!");
}
}
public function keys() {
$this->_checkCallback();
return array_keys($this->_members);
}
public function length() {
$this->_checkCallback();
return sizeof($this->_members);
}
public function exists($key) {
$this->_checkCallback();
return (isset($this->_members[$key]));
}
/**
* Use this method to define a function to be
* invoked prior to accessing the collection.
* The function should take a collection as a
* its sole parameter.
*/
public function setLoadCallback($functionName, $objOrClass = null) {
if($objOrClass) {
$callback = array($objOrClass, $functionName);
} else {
$callback = $functionName;
}
//make sure the function/method is valid
if(!is_callable($callback, false, $callableName)) {
throw new Exception("$callableName is not callable " .
"as a parameter to onload");
return false;
}
$this->_onload = $callback;
}
/**
* Check to see if a callback has been defined and if so,
* whether or not it has already been called. If not,
* invoke the callback function.
*/
private function _checkCallback() {
if(isset($this->_onload) && !$this->_isLoaded) {
$this->_isLoaded = true;
call_user_func($this->_onload, $this);
}
}
}
所需的Student如下：
復制代碼 代碼如下:
class CourseCollection extends Collection {
public function addItem(Course $obj,$key=null) {
parent::addItem($obj,$key);
}
}
class Student{
private $_id;
private $_name;
public $course;
public function __construct($id,$name)
{
$this->_id=$id;
$this->_name=$name;
$this->course=new CourseCollection();
$this->course->setLoadCallback('loadCourses',$this);
}
public function getName()
{
return $this->_name;
}
public function getID()
{
return $this->_id;
}
public function __toString()
{
return $this->_name;
}
public function loadCourses(Collection $col)
{
$col->addItem(new Course(1, "001", "語文"),1);
$col->addItem(new Course(2, "002", "數學"),2);
}
}
調用代碼如下：
$student=new Student(1, "majiang");
print $student->getName();
print $student->course->getItem(1);
php技術：淺析PHP中Collection 類的設計，轉載需保留來源！
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