简单谈谈PHP面向对象之标识对象

标识对象模式

这个模式主要功能就是创建sql语句中的wehre条件字符串的，下面直接看代码和注释：

namespace woomapper;

//字段对象
class Field {
  protected $name = null;     //字段名称
  protected $operator = null;     //操作符  
  protected $comps = array();     //存放条件的数组  
  protected $incomplete = false;   //检查条件数组是否有值

  function __construct ($name){
    $this->name= $name;
  }

  //添加where 条件
  function addTest($operator,$value){
    $this->comps[] = array('name'=>$this->name,'operator'=>$operator,'value'=>$value);
  }

  //获取存放条件的数组
  function getComps(){
    return $this->comps;
  }

  function isIncomplete(){
    return empty($this->comps);
  }
}

//标识对象
class IdentityObject {
  protected $currentfield = null;    //当前操作的字段对象
  protected $fields = array();    //字段集合
  private $and = null;
  private $enforce = array();      //限定的合法字段    

  function __construct($field = null, array $enforce = null){
    if(!is_null($enforce)){
      $this->enforce = $enforce;
    }
    if(!is_null($field)){
      $this->field($field);
    }
  }

  //获取限定的合法字段
  function getObjectFields(){
    return $this->enforce;
  }

  //主要功能为设置当前需要操作的对象
  function field($fieldname){
    if(!$this->isVoid()&& $this->currentfield->isIncomplete()){
      throw new Exception("Incomplete field");
    }
    $this->enforceField($fieldname);
    if(isset($this->fields[$fieldname]){
      $this->currentfield = $this->fields[$fieldname];
    } else {
      $this->currentfield = new Field($fieldname);
      $this->fields[$fieldname] = $this->currentfield;
    }
    return $this;          //采用连贯语法
  }

  //字段集合是否为空
  function isVoid(){
    return empty($this->fields);
  }

  //检查字段是否合法
  function enforceField ($fieldname){
    if(!in_array($fieldname,$this->enforce) && !empty($this->enforce)){
      $forcelist = implode(',',$this->enforce);
      throw new Exception("{$fieldname} not a legal field {$forcelist}");
    }
  }

  //向字段对象添加where条件
  function eq($value){
    return $this->operator("=",$value);
  }

  function lt($value){
    return $this->operator("<",$value);
  }

  function gt($value){
    return $this->operator(">",$value);
  }

  //向字段对象添加where条件
  private function operator($symbol,$value){
    if($this->isVoid){
      throw new Exception("no object field defined");
    }
    $this->currentfield->addTest($symbol,$value);
    return $this;                   //采用连贯语法
  }

  //获取此类中所有字段对象集合的where条件数组
  function getComps(){
    $ret = array();
    foreach($this->fields as $key => $field){
      $ret = array_merge($ret,$field->getComps());
    }
    return $ret;
  }
}

//客户端代码
$idobj = new IdentityObject ();
$idobj->field("name")->eq("The Good Show")->field("start")->gt(time())->lt(time()+(24*60*60));
$test = $idobj->getComps();
var_dump($test);

//输出类似下面的内容

/*
array{
  array('name'=>'name','operator'=>'=','value'=>'The Good Show'),
  array('name'=>'start','operator'=>'>','value'=>'123456'),  //123456表示time()函数输出的时间戳
  array('name'=>'start','operator'=>'<','value'=>'123456')
}

*/

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