Rails图像URL验证 [英] Rails Image URL Validation

问题描述

比方说，我在一个表中有记录，每个记录都有一个icon属性，该属性采用以下形式的url:

Let's say I have records in a table, and each has an icon attribute that takes a url of the form:

• balls/x.png
• balls/y.png
• balls/z.png
• …

如何编写验证，以确保网址以"balls/"开头，并以.png，.gif结尾.还是.jpg?

How do I write a validation that makes sure the url starts with "balls/" and ends with either .png, .gif. or .jpg?

我当前的验证只是检查文件扩展名:

My current validation just checks for the file extension:

validates_format_of :icon, :with => %r{\.(gif|jpg|png)$}i, :message => 'must be a URL for GIF, JPG ' + 'or PNG image.'

推荐答案

如何编写验证，以确保网址以"balls/"开头，并以.png，.gif结尾.还是.jpg?

How do I write a validation that makes sure the url starts with "balls/" and ends with either .png, .gif. or .jpg?

这将起作用:

validates_format_of :icon,
  :with    => %r{^balls/.+\.(gif|jpe?g|png)$}i,
  :message => "must start with 'balls/' and have an image extension"

但是您可以在同一字段上进行多个验证.因此，这也将起作用，并且更具可读性:

But you can have multiple validations on the same field. So, this will work too, and is more readable:

validates_format_of :icon,
  :with    => %r{^balls/.+}i,
  :message => "must start with 'balls/' and have a filename"

validates_format_of :icon,
  :with    => %r{\.(gif|jpe?g|png)$}i,
  :message => "must have an image extension"

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