类默认公共变量可以从 php 中的数组动态定义吗？

Question

我有一个事件类，用于将数据插入/更新到我的数据库中。有没有一种方法可以从 db_fields 数组创建公共变量，这样我就不必复制数据？

这是我目前有效的结构......

class event{
    protected static $table_name='tName';
    protected static $db_fields = array('field1','field2','field3','field4','field5');

    public $field1;
    public $field2;
    public $field3;
    public $field4;
    public $field5;
}

我想要有这样的东西..

class event{
    protected static $table_name='tName';
    protected static $db_fields = array('field1','field2','field3','field4','field5');

    function __construct() {
        create_public_vars_here($db_fields);
    }

}

谢谢！

Answer 1

您可以尝试以下操作：

class event{

    protected static $table_name='tName';
    protected static $db_fields = array('field1','field2','field3','field4','field5');

    function __construct() {
        foreach (self::$db_fields as $var) {
            $this->$var = $whateverDefaultValue;
        }
        // After the foreach loop, you'll have a bunch of properties of this object with the variable names being the string values of the $db_fiels.
        // For example, you'll have $field1, $field2, etc and they will be loaded with the value $whateverDefaultValue (probably want to set it to null).
    }

}

.

Answer 2

您可以使用魔术设置器/获取器：

class event{

    protected static $table_name='tName';
    protected static $db_fields = array('field1','field2','field3','field4','field5');

    public function __get($key)
    {

        if(!in_array($key, static::$db_fields))
            throw new Exception( $key . " doesn't exist.");

        return $this -> $key;

    }

    public function __set($key, $value)
    {

        if(!in_array($key, static::$db_fields))
            throw new Exception( $key . " doesn't exist.");

        $this -> $key = $value;

    }   

}

这样你就可以确保不会达到列表之外的值：

$event -> field1 = 'hello';  // --> OK
$event -> field17 = 'hello'; // --> Exception: field17 doesn't exist

echo $event -> field1;  // --> OK
echo $event -> field17; // --> Exception: field17 doesn't exist

至于在代码中明确的公共变量声明，只要您不必迭代对象，就不需要 - 但在这种情况下，您将实现 Iterator 基于您的静态字段的界面。

Answer 3

使用突变分子：

class event{
  protected static $table_name='tName';
  protected static $db_fields = array('field1','field2','field3','field4','field5');

  function getVars($var) {
    if(!in_arrary($this->db_fields[$var])) {
      return false;
    } else {
      return $this->db_fields[$var];
    }
  }
}

.

然后您可以如下访问它：

$eventObject->getVars('field3');

.

或者，如果您没有从类中创建对象：

event::getVars('field3');

.

编辑：从复杂的东西的精神使您没有违规，代码添加了。