Ruby on rails Rails图像URL验证

假设我在一个表中有记录，每个记录都有一个图标属性，该属性采用以下形式的url：

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

如何编写验证，确保url以“balls/”开头，以.png、.gif结尾。还是.jpg

我当前的验证仅检查文件扩展名：

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

---

直接的正则表达式怎么样，比如：

validates_format_of :icon, :with =>  %r{^(balls\/)[A-Za-z]+\.(gif|jpg|png)$}i, :message => 'icon must start with balls'

---

直接的正则表达式怎么样，比如：

validates_format_of :icon, :with =>  %r{^(balls\/)[A-Za-z]+\.(gif|jpg|png)$}i, :message => 'icon must start with balls'

如何编写验证，确保url以“balls/”开头，以.png、.gif结尾。还是.jpg

这将有助于：

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，这也会起作用，并且更具可读性：

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"

如何编写验证，确保url以“balls/”开头，以.png、.gif结尾。还是.jpg

这将有助于：

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，这也会起作用，并且更具可读性：

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"