A detailed description of late static binding in Laravel-PHP Tutorial-php.cn

A detailed description of late static binding in Laravel

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Release： 2023-03-19 17:32:02

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Regarding PHP's new static delayed static binding, or late static binding, I encountered a usage problem in Laravel. This article mainly introduces a brief discussion of a late static binding in Laravel. The editor thinks it is quite good, so I will share it with you now and give it as a reference. Let’s follow the editor to take a look, I hope it can help everyone.

As follows, when calling the Model in Laravel to add new data, first add a method to the Model to obtain the sub-table:

protected function addToMessage($msgType, $userID, $commentID, $replyCommentID, $replyUserID, $gameID)
{
  if (!$userID) {
    return false;
  }
 
  $table = &#39;t_message_&#39; . hashID($userID, 100);
  $this->message->setTable($table)->create([
    &#39;msg_type&#39;     => $msgType,
    &#39;user_id&#39;     => $userID,
    &#39;comment_id&#39;    => $commentID,
    &#39;reply_comment_id&#39; => $replyCommentID,
    &#39;reply_user_id&#39;  => $replyUserID,
    &#39;game_id&#39;     => $gameID,
    &#39;is_read&#39;     => 0,
    &#39;created_at&#39;    => date(&#39;Y-m-d H:i:s&#39;),
  ]);
  return true;
}

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Here is the setTable method It is the method defined in the Model to obtain the sub-table:

public function setTable($table)
{
  $this->table = $table;
  return $this;
}

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It was found from the error log that $this->table did not take effect, but the create method was actually called. When the table name was printed before, it was the expected value. Why is $this->table not reset when the create method is called here?

Here $this->message is a model class that inherits the Model class, where the create method:

public static function create(array $attributes = [])
{
  $model = new static($attributes);
 
  $model->save();
 
  return $model;
}

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is located in vendor\laravel\framework\src \Illuminate\Database\Eloquent\Model.php Line 557.

Because the Model class of the Laravel framework is an abstract type, the abstract class in PHP can be instantiated using new static late static binding, and create In the method, $model = new static($attributes) is actually re-instantiated and returned, but the caller's Model class does not define the table attribute, so $this->table has no value at this time.

The solution is to use the save method, as shown in the figure. In fact, the create method also calls the save method.

Experiment

An abstract class A has a create method, which is instantiated and returned through delayed static binding. Class B inherits A, and the name attribute of the parent class is modified in the test method.

<?php
 
abstract class A
{
  protected $name = "tanteng";
 
  public static function create()
  {
    return new static();
  }
}
 
class B extends A
{
  //protected $name = &#39;纸牌屋弗兰克&#39;;
 
  public function test()
  {
    $this->name = "Tony Tan";
    return $this;
  }
}
 
$obj1 = (new B)->test();
$obj2 = (new B)->test()->create();
var_dump($obj1);
var_dump($obj2);

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The results show that both instances $obj1 and $obj2 are instances of B. The attribute name has changed by calling the test method, but after calling the create method, the name attribute has not changed. No change. This is the scene encountered in Lavarel mentioned in this article. (If the comment is turned on here, the printed name is the rewritten value)

If the abstract class A is changed to a normal class, and new static is changed to new self for instantiation, the result will be different, the printed The attribute name is an attribute of the respective class.

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