A brief analysis of the design of Collection class in PHP_PHP Tutorial

I have been developing with .net for many years. I recently came into contact with php and found that php is also very fun. However, I found that there is no Collection class in it, only arrays, and arrays are very powerful. Here I use an array to wrap it into a Collection. The code is as follows:

Copy code The code is as follows:

class Collection{
private $_members=array();

public function addItem($obj,$key=null)
{
if($key)
if(isset ($this->_members[$key]))
                                                                                                                                                                                                    🎜>              $this->_members[$key]=$obj;
                                                                  gt;_members[]=$obj;
}
}

public function removeItem($key)
{
if(isset($this->_members[$key]))
{
unset( $this->_members[$key]);
                                                                                                                           
public function getItem($key)
{
if(isset($this->_members[$key]))
{
return $this->_members[$key] ];
}
else
{
throw new exception("Invalid Key "$key"!"); Keys( )
                                                                                                                                                                                                                                                                      ;     );
}

public function exists($key)
{
return (isset($this->_members[$key]));
}
}


Now let’s test whether this collection is easy to use.
We first create a collection element class Course:



Copy the code

The code is as follows:

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;
    }
}

测试代码如下：
$courses=new Collection();
$courses->addItem(new Course(1, "001", "语文"),1);
$courses->addItem(new Course(2, "002", "数学"),2);
$obj=$courses->getItem(1);
print $obj;
我想这个集合类应该可以满足我们平日开发的需求了吧。
可是我们现在。net里面有个对象延迟加载，举个例子来说吧，假如现在有Student这个对象，它应该有很多Course，但是我们希望在访问Course之前Course是不会加载的。也就是说在实例化Student的时候Course个数为0，当我们需要Course的时候它才真正从数据库读取相应数据。就是需要我们把Collection做成惰性实例化。
修改后的Collection代码如下：

复制代码 代码如下:

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：

复制代码 代码如下:

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", "语文"),1);
        $col->addItem(new Course(2, "002", "数学"),2);
    }
}

调用代码如下：
$student=new Student(1, "majiang");
print $student->getName();
print $student->course->getItem(1);

http://www.bkjia.com/PHPjc/327791.htmlwww.bkjia.comtruehttp://www.bkjia.com/PHPjc/327791.htmlTechArticle用.net开发已经很多年了，最近接触到php，发现php也很好玩。不过发现它里面没有集合Collection类，只有数组，并且数组很强。这里我用数组来...