用。net開發已經很多年了，最近接觸到php，發現php也很好玩。不過發現它里面沒有集合Collection類，只有數組，并且數組很強。這里我用數組來包裝成一個集合Collection，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：

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：

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 = $functionName;}//make sure the function/method is validif(!is_callable($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：

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);

?

轉載于:https://www.cnblogs.com/majiang/archive/2012/11/23/2783779.html

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