PHP中如何仅在需要时加载变量

发布于 2024-10-05 06:34:12 字数 642 浏览 5 评论 0原文

我有一个具有多个公共属性的类，其对象在系统的不同部分中使用。问题是，我只需要在使用类对象的每个位置加载其中一些公共属性，因为每次加载整个属性列表都将花费很长时间。

有什么方法可以使用 __autoload 或类似的函数来调用在调用时加载不同变量的函数吗？

例如

class Bread {
  public 
    $Ingredients,
    $Price,
    $Color;

  public function magicLoading($var) {
    switch($var) {
      case "Ingredients" : return loadIngredients();
      case "Price"       : return loadPrice();
      case "Color"       : return loadColor();
      default            : break;
    }
  }

  public function loadIngredients() {
    $this->Ingredients = ...
  }
}

foreach($Bread->Ingredients as $Ingredient) {
  //do stuff here
}

原文

I have a class with multiple public properties whose objects are being used in different parts of the system. The problem is that I need to load only some of those public properties in each place I'm using the objects of the class, because loading the entire list of properties every time would take forever.

Is there any way I can use __autoload or a similar function to call the functions that load different variables at the time they are called?

E.g.

class Bread {
  public 
    $Ingredients,
    $Price,
    $Color;

  public function magicLoading($var) {
    switch($var) {
      case "Ingredients" : return loadIngredients();
      case "Price"       : return loadPrice();
      case "Color"       : return loadColor();
      default            : break;
    }
  }

  public function loadIngredients() {
    $this->Ingredients = ...
  }
}

foreach($Bread->Ingredients as $Ingredient) {
  //do stuff here
}

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何处潇湘 2024-10-12 06:34:12

在您的代码中，

将函数 magicLoading 重命名为 __get，
在“load...”方法中添加 return 语句，
检查变量是否具有尚未初始化。

它有效！

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樱花落人离去 2024-10-12 06:34:12

向我的同事道歉，因为他们发布了看似重复的答案，但他们错过了一些东西。

为了使 __get() 和 __set() 挂钩正常工作，所涉及的成员变量根本不能被声明 - 只是声明但未定义是不够的。

这意味着您必须删除您希望以这种方式访问的任何变量的声明（即 public $Ingredients; 等），

因此，您的类可能如下所示。

class Bread
{
  /* No variable declarations or the magic methods won't execute */

  protected function loadIngredients()
  {
    $this->Ingredients = ...
  }

  public function __get( $var )
  {
    switch( $var )
    {
      case "Ingredients" : $this->loadIngredients(); break;
      case "Price"       : $this->loadPrice(); break;
      case "Color"       : $this->loadColor(); break;
      default            : throw new Exception( "No case for $var" );
    }
    return $this->$var;
  }
}

Apologies to my colleagues for posting what looks like a duplicate answer, but they have missed something.

In order for the __get() and __set() hooks to function properly, the member variable in question cannot be declared at all - simply being declared but undefined isn't sufficient.

This means you'll have to remove the declaration of any variables you want to be accessible in this way (i.e., the public $Ingredients; etc)

Ergo, your class might then look like this.

class Bread
{
  /* No variable declarations or the magic methods won't execute */

  protected function loadIngredients()
  {
    $this->Ingredients = ...
  }

  public function __get( $var )
  {
    switch( $var )
    {
      case "Ingredients" : $this->loadIngredients(); break;
      case "Price"       : $this->loadPrice(); break;
      case "Color"       : $this->loadColor(); break;
      default            : throw new Exception( "No case for $var" );
    }
    return $this->$var;
  }
}

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