如何在域驱动设计中的表单和值对象之间共享验证？ [英] How to share validation between Forms and Value Objects in Domain Driven Design?

问题描述

<强>＃1。验证表单上的EmailAddress

我有一个后端表单类，其中包含验证的 emailAddress 属性逻辑，以便我可以将错误消息返回给用户。我验证了所有表单输入，如：

  $ form-> fillWith（$ request-> input（））; 
 
 if（$ form-> validate（））{
 $ form-> dispatch（$ command）; //如果同步，form接受命令的messageBag 
} 
 
返回响应（$ form-> getMessageBag（） - > toJson（））; 
  

＃2。验证命令处理程序中的EmailAddress值对象

我有一个命令处理程序，它将采用原始字符串email并创建一个值对象。如果电子邮件无效，value对象将在创建时抛出异常：

  public function handle（$ command）{
 
尝试{
 $ emailAddress = new ValueObjects \EmailAddress（$ command-> emailAddress）; 
 
 //创建更多值对象... 
 
 //对域做些其他的事情... 
 
} catch（DomainException $ e ）{
 $ this-> messageBag-> add（errors，$ e-> getMessage（））; 
} catch（\Exception $ e）{
 $ this-> messageBag-> add（errors，unexpected error）; 
} 
 
返回$ this-> messageBag; 
 
 $ / code> 

在＃1中，我想在发送命令之前尽早捕获验证。但是在＃2中，当我构建VO时验证逻辑会重复。

我有这些问题：

• 如果我需要更改电子邮件的验证要求地址，那么我必须更新这两个地方。


• 如果我在表单上使用了VO，那么在传递给命令时我将不得不再次解构它们。另外，如果我的表单处于不同的有界上下文中，那么我将会有VO从另一个有界上下文中泄漏域（可能这是必要的？）。
  
  
  

  所以我的问题是，我应该创建一些验证器对象，以便我的表单验证和VO可以共享/使用？或者如何捕获表单和值对象之间的重复验证问题？

  解决方案

将验证逻辑封装为可重用类。这些类通常称为规格，验证器或规则，是域的一部分。

有多种方式可以做到这一点，这里有一个我使用的方法：

1. 定义提供 bool IsSatisifed（）方法的接口 Specification 。


2. 为特定的值对象实现此接口，例如 EmailWellformedSpec 。


3. 使用规范作为先决条件在域中执行业务规则（即违规总是编程错误） / li>
   
4. 将规范用于服务层中的输入输入验证（即违规是用户错误）。
   

如果您想将多个规格组合到一个更大的规格，规范模式是一个很好的做法。请注意，如果使用该模式，则需要通过构造函数传递数据，但这不是问题，因为规范类通常很简单。

#1. Validate EmailAddress on the Form

I have a backend form class with an emailAddress property that has validation logic so that I can return an error message back to the user. I validate all form inputs with something like:

$form->fillWith($request->input());

if($form->validate()){
    $form->dispatch($command); // if synchronous, form takes command's messageBag
}

return response($form->getMessageBag()->toJson());

#2. Validate EmailAddress Value Object in the Command Handler

I have a command handler that will take the primitive string email and create a value object. The value object will throw an exception on creation if the email is invalid:

public function handle($command){

   try {
      $emailAddress = new ValueObjects\EmailAddress($command->emailAddress);

      // create more value objects...

      // do something else with the domain...

   } catch (DomainException $e) {
        $this->messageBag->add("errors", $e->getMessage());
   } catch (\Exception $e) {
        $this->messageBag->add("errors", "unexpected error");
   }

   return $this->messageBag;
}

In #1, I want to capture validation early before I dispatch a command. But then in #2 that validation logic is repeated when I build VOs.

Issues I have:

• If I need to change validation requirements on email addresses, then I have to update both places.
• If I use VOs on my form then I will have to deconstruct them again when passing to the command. Also, if my form is in a different Bounded Context then I will have VOs leaking domain from the other Bounded Context (maybe this is necessary?).

So my question is, should I create some validator objects that both my form validation and VOs can share/utilize? Or how do I capture repeated validation concerns between forms and value objects?

解决方案

Encapsulate the validation logic into a reusable class. These classes are usually called specifications, validators or rules and are part of the domain.

There are multiple ways of doing this, here is an approach that I use:

1. Define an interface Specification that provides a bool IsSatisifed() method.
2. Implement this interface for a specific value object, e.g. EmailWellformedSpec.
3. Enforce the business rule within the domain by using the spec as precondition (i.e. violation is always a programming error).
4. Use the spec for input input validation in the service layer (i.e. violation is a user error).

If you want to combine multiple specs to a larger one, the Specification Pattern is a good approach. Note that you need to pass in the data through the constructor if you use that pattern, but this is not a problem because the specification classes are usually simple.

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