了解 Rails 验证:allow_blank 有什么作用? [英] Understanding Rails validation: what does allow_blank do?

问题描述

我对 Rails 很陌生，发现了一个小片段来逐步验证存在性和唯一性:首先检查存在性，然后检查唯一性.

I'm quite new to Rails and found a little snippet to validate presence and uniqueness step by step: first check presence, then check uniqueness.

validates :email, :presence => true, :allow_blank => true, :uniqueness => { :case_sensitive => false }

我对使用 presence => 有点困惑true 和 allow_blank =>真的在一起.

I'm a little bit confused about using presence => true and allow_blank => true together.

不使用 allow_blank =>true 两条规则会同时检查，而不是一步一步检查.

Without using allow_blank => true both rules will be checked at the same time and not step by step.

为什么 allow_blank =>真的会变魔术吗?

推荐答案

您所拥有的与此等效(为了清晰起见，已封装):

What you've got is equivalent to this (wrapped for clarity):

validates :email, :presence => true, 
            :uniqueness => { :allow_blank => true, :case_sensitive => false }

虽然这有点愚蠢，因为如果您需要存在，那么这将无效":allow_blank 子句到 :uniqueness.

That's a little silly though since if you're requiring presence, then that's going to "invalidate" the :allow_blank clause to :uniqueness.

当您切换到使用其他验证器时更有意义.. 比如说... format 和 uniqueness，但是如果它是空白的，您就不需要任何检查.在这种情况下，添加全局应用":allow_blank 更有意义，DRY 对代码进行了一些改进.

It makes more sense when you switch to using other validators.. say... format and uniqueness, but you don't want any checks if it's blank. In this case, adding a "globally applied" :allow_blank makes more sense and DRY's up the code a little bit.

这...

validates :email, :format => {:allow_blank => true, ...}, 
                  :uniqueness => {:allow_blank => true, ...}

可以写成:

validates :email, :allow_blank => true, :format => {...}, :uniqueness => {...}

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