Laravel 5 Eloquent，如何动态设置强制转换属性
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Laravel 5 Eloquent, How to set cast attribute dynamically
提问by antoniputra
In laravel 5.1 there is new feature called Attribute Casting, well documented at here : http://laravel.com/docs/5.1/eloquent-mutators#attribute-casting
在 laravel 5.1 中有一个名为 Attribute Casting 的新功能，这里有详细记录：http: //laravel.com/docs/5.1/eloquent-mutators#attribute-casting
My question is, it is possible to make attribute casting dynamically ?
我的问题是，可以动态进行属性转换吗？
for example, I have a table with columns :
例如，我有一个带有列的表：
id | name | value | type |
1 | Test_Array | [somearray] | array |
2 | Test_Boolean | someboolean | boolean |
it is possible to set valueattribute cast, depends on typefield, that work both in write(create/update) and fetch ?
可以设置value属性转换，取决于type字段，在 write(create/update) 和 fetch 中都有效？
回答by jedrzej.kurylo
You'll need to overwrite Eloquent model's getCastType()method in your model class:
您需要在模型类中覆盖Eloquent模型的getCastType()方法：
protected function getCastType($key) {
if ($key == 'value' && !empty($this->type)) {
return $this->type;
} else {
return parent::getCastType($key);
}
}
You'll also need to add valueto $this->castsso that Eloquent recognizes that field as castable. You can put the default cast there that will be used if you didn't set type.
您还需要为$this->casts添加值，以便 Eloquent 将该字段识别为castable。如果您没有设置type，您可以将默认演员表放在那里。
Update:
更新：
The above works perfectly when reading data from the database. When writing data, you have to make sure that typeis set before value. There are 2 options:
从数据库读取数据时，上述方法完美无缺。写入数据时，您必须确保在value之前设置type。有2个选项：
Always pass an array of attributes where typekey comes before valuekey - at the moment model's fill()method respects the order of keys when processing data, but it's not future-proof.
Explicitely set typeattribute before setting other attributes. It can be easily done with the following code:
$model == (new Model(['type' => $data['type']))->fill($data)->save();
始终传递类型键在值键之前的属性数组- 目前模型的fill()方法在处理数据时尊重键的顺序，但它不是面向未来的。
在设置其他属性之前显式设置类型属性。可以使用以下代码轻松完成：
$model == (new Model(['type' => $data['type']))->fill($data)->save();
回答by patricus
The $castsattribute it used whenever you access a field, not when it is fetched from the database. Therefore, you can update the $castsattribute after the model has been populated, and it should work fine whenever you access the valuefield. You just need to figure out how to update the $castsattribute when the typefield is changed.
$casts每次访问字段时使用的属性，而不是从数据库中获取时使用的属性。因此，您可以$casts在填充模型后更新属性，并且无论何时访问该value字段它都应该可以正常工作。您只需要弄清楚如何$casts在type字段更改时更新属性。
One potential option would be to override the fill()method so that it calls the parent fill()method first, and then updates the $castsattribute with the data in the typefield.
一种可能的选择是覆盖该fill()方法，以便它首先调用父fill()方法，然后$casts使用type字段中的数据更新属性。
Another potential option would be to abuse the mutator functionality, and create a mutator on the typefield, so that whenever it changes, it would update the $castsattribute.
另一个可能的选择是滥用 mutator 功能，并在type字段上创建一个 mutator ，以便每当它发生变化时，它都会更新$casts属性。
