validates_attachment为可选字段

问题描述：

我有一个可选的uload字段，可以将其保留为空.但是，当使用它时，我想验证附件的大小和内容.因此，我在模型中使用了此验证:

I have an uload field which is optional, it can be left empty. But when it is is used, I want to validate the size and content of the attachment. So I use this validation in the model:

validates_attachment :attachment, content_type: { content_type: ["image/jpeg", "image/gif", "image/png"] }, size: { in: 0..500.kilobytes }

这在有附件的情况下有效，但在保留为空的情况下将失败.如何确保仅在有附件的情况下验证?

This works when there is an attachment, but fails when it is left empty. How can I make sure it only validates when there is an attached file?

此处提到的解决方案不幸地无法正常工作.

The solutions mentioned here are not working unfortunately.

答

您提供的链接可以为您提供我的建议-使用if:参数

The link you provided is giving you what I would suggest - using the if: argument

if:

在验证中使用if: 基本上可以让您确定验证器将触发的条件.我从链接中看到，伙计们正在使用if: :avatar_changed?

您可能遇到的问题是可以使用Proc或instance method确定条件；而且这些人正在avatar上使用一种方法(尽管是内置方法)，所以不太可能产生想要的结果.

The problem you've likely encountered is you can either use a Proc or instance method to determine the condition; and as these guys are using a method on avatar (albeit an inbuilt one), it's not likely going to yield the result you want.

我会这样做:

validates_attachment :attachment, content_type: { content_type: ["image/jpeg", "image/gif", "image/png"] }, size: { in: 0..500.kilobytes }, if: Proc.new {|a| a.attachment.present? }

这基本上确定了attachment对象是否存在，向验证提供true或false

This basically determines if the attachment object is present, providing either true or false to the validation

validates_attachment为可选字段

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