验证跨越多个字段 [英] Validation spanning multiple fields

问题描述

我正在尝试应用表单，并且一直在想如何实现一个验证依赖于其他字段的字段的表单。例如一个注册表单，其中密码和 confirm_password 字段，我想验证密码== confirm_password 。

在表单运行后，我可以在处理程序中完成，但这意味着会丢失错误消息。

编辑：忘了提及，我主要使用Yesods应用表单，但它们似乎与消化函数相当接近 p>

解决方案

您使用的是什么类型的表单系统？您可以使用消化函数轻松做到这一点，以下是我的一个注册表格示例：

  registrationForm = 
注册
< $> username。：text Nothing 
< *> password。：passwordConfirmer 
 where passwordConfirmer = 
 validate fst'$（，）< $> （p1。：text nothing）
 * （p2。：text Nothing）
 fst'（p1，p2）| p1 == p2 =成功p1 
 |否则=错误密码必须匹配
  

在这里您可以看到我为密码字段通过使用我的 passwordConfirmer 表单字段。这个字段使用2个文本字段并将它们放入一个元组中，但验证后只需要 fst 元素（尽管它可能需要 snd $ b $ My 注册类型是： p>



  data注册=注册
 {regUserName :: Text 
，regPassword :: Text 
} 
  




I'm trying to grok applicative forms, and I've been wondering how to implement a form that validates fields that depend on other fields. For example a registration form which has password and confirm_password fields and I'd like to validate that password == confirm_password.

I could be done after the form has ran, in the handler, but that would mean losing error messages.

Edit: Forgot to mention, I'm mainly using Yesods applicative forms, but they seem to be quite close to digestive-functors

解决方案

What type of form system are you using? You can easily do this with digestive-functors, here's an example of one of my registration forms:

registrationForm =
    Registration
      <$> "username" .: text Nothing
      <*> "password" .: passwordConfirmer
  where passwordConfirmer =
          validate fst' $ (,) <$> ("p1" .: text Nothing)
                              <*> ("p2" .: text Nothing)
        fst' (p1, p2) | p1 == p2  = Success p1
                      | otherwise = Error "Passwords must match"

Here you can see I generate a value for my 'password' field by using my passwordConfirmer form field. This field uses 2 text fields and puts them into a tuple, but after validation it just takes the fst element (though it could take snd, we've guaranteed they are equal!).

My Registration type is:

data Registration = Registration
    { regUserName :: Text
    , regPassword :: Text
    }

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