Rails:如何仅在存在值时验证格式? [英] Rails: How to validate format only if value is present?

问题描述

我想验证表单值的格式，允许空值或需要特定格式.

I would like to validate the format of a form value, allowing an empty value or requiring a specific format.

要根据格式验证值，这可以正常工作:

To validate a value against a format, this works fine:

validates :application_bundle_identifier, :format => {
  :with => /^[a-zA-Z0-9.-]+$/,
  :message => "A bundle identifier should contain only alphanumeric (A-Z,a-z,0-9), hyphen (-), and period (.) characters."
}

现在，我想允许用户根本不输入该值.在这种情况下，我可以将正则表达式调整为 ^[a-zA-Z0-9.-]*$，但这似乎不是一个很好的 Rails 方式.根据格式的不同，这可能是不可能的，或者至少不太清楚.

Now, I would like to allow users to not enter the value at all. In this case, I could tweak the regexp to ^[a-zA-Z0-9.-]*$, but this does not seem a very good Rails-way. Depending of the format, it might be not possible, or at least less clear.

这种情况下的最佳做法是什么?

What is the best practice in this case?

推荐答案

当属性为空/空/nil 时，您可以使用选项allow_blank: true 跳过验证.

You can use the option allow_blank: true to skip the validation when the attribute is blank/empty/nil.

https://guides.rubyonrails.org/active_record_validations.html#allow-blank

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