导轨：验证一个字段是present只有一个是present [英] Rails: validating a field is present only if another is present

问题描述

我有一个模型，其中有两个字段，可以从技术上为空。字段名：is_activated 和：activated_at 。 ：activated_at 只需要当：is_activated 设置为真。它并不需要是present如果：is_activated 是假。什么是Rails中的适当的方式直接设置此验证到的ActiveRecord？

解决方案

您可以使用的 PROC上的：activated_at 验证

 验证：activated_at，：presence，如果：Proc.new {| A | a.is_activated？ }
 

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推荐阅读：

• 的http://guides.rubyonrails.org/active_record_validations.html#using-a-proc-with-if-and-unless
• 的http://api.rubyonrails.org/classes/ActiveRecord/Validations/ClassMethods.html

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最后，你应该考虑重新命名：is_activated 简单地：激活。这被认为是Rails中更好的做法。该是_ preFIX用在其他语言的布尔类型的属性，因为它们的方法名称不支持？字符。红宝石呢，和Rails生成 ___？对布尔属性的方法。正因为如此，最好只调用属性：激活并检查启动 的<？。 / P>

I have a model where there are two fields that can technically be null. The field names are :is_activated and :activated_at. :activated_at is only required if :is_activated is set to true. It does not need to be present if :is_activated is false. What's the appropriate way in Rails to set this validation directly into ActiveRecord?

解决方案

You can use a Proc on the :activated_at validator.

validates :activated_at, :presence, if: Proc.new { |a| a.is_activated? }

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Recommended Reading:

• http://guides.rubyonrails.org/active_record_validations.html#using-a-proc-with-if-and-unless
• http://api.rubyonrails.org/classes/ActiveRecord/Validations/ClassMethods.html

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Finally, you should consider renaming :is_activated to simply :activated. This is considered better practice in Rails. The is_ prefix is used in other languages for boolean attributes because their method names don't support a ? character. Ruby does, and Rails generates ___? methods on boolean attributes. Because of this it's better to just call the attribute :activated and check it with activated?.

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