error_messages_for

Friendlier error message example

The default error messages can be a bit stale and off putting. Try somethings like this:

error_messages_for(
  :user, 
  :header_message => "Oops - We couldn't save your user!", 
  :message => "The following fields were a bit of a problem:", 
  :header_tag => :h1
)

You can also use error_messages_for as follows

<%  form_for User.new do |f| %>
  <%=  f.error_messages :header_message => "..." %>
<%  end  %>

Overriding the default div class="fieldWithErrors"

By default fields that are invalid are wrapped in:

<div class="fieldWithErrors">
  <input type="text" name="blah">
</div>

To override and wrap in spans instead of divs place the following in your environment.rb:

ActionView::Base.field_error_proc = Proc.new { |html_tag, instance| "<span class=\"fieldWithErrors\">#{html_tag}</span>" }

or to not use wrapping at all:

ActionView::Base.field_error_proc = Proc.new { |html_tag, instance| "#{html_tag}" }

Customizing attribute names in error messages

By default, the error messages translate the names of the attributes through String#humanize. The way to to change that is to override the ActiveRecord::Base.human_attribute_name method.

For example, if you want to name a column in your database as :www_url and you want to say “Website” instead of “Www url” in the error message, you can put this into your model:

class Person < ActiveRecord::Base
  def self.human_attribute_name(attribute_key_name)
    if attribute_key_name.to_sym == :www_url
      "Website"
    else
      super
    end
  end
end

Currently this seems to be the cleanest and easiest way. Unfortunately, human_attribute_name is deprecated and may stop working in a future release of Rails.

Override fieldWithErrors markup in Rails > v2

The code posted by @hosiawak will still work in recent versions of Rails, but maybe a more current, idiomatic way to do it is to stick this inside the Rails::Initializer block in environment.rb (obviously you’ll also need to restart your server to pick up the config change):

config.action_view.field_error_proc = Proc.new {|html_tag, instance| 
  %(<span class="fieldWithErrors">#{html_tag}</span>)}

Detailed messages for a nested model

Detailed messages for a nested model

<%@address = @order.address%>
<%=error_messages_for :address%>

re: Customizing attribute names in error messages

You can use Module.alias_attribute to achieve the same result as overriding human_attribute_name. After aliasing use the new name in the validates_xxxx_of methods or ActiveRecord::Errors.add.

Use Hpricot to customise error fields

I like to use Hpricot to add error information to my form fields. Here’s an example:

ActionView::Base.field_error_proc = Proc.new do |html_tag, instance|
  if html_tag =~ /<(input|label|textarea|select)/
    error_class = 'error'
    nodes = Hpricot(html_tag)
    nodes.each_child { |node| node[:class] = node.classes.push(error_class).join(' ') unless !node.elem? || node[:type] == 'hidden' || node.classes.include?(error_class) }
    nodes.to_html
  else
    html_tag
  end
end

This will only apply the CSS class ‘error’ to elements that aren’t hidden inputs and don’t already have the error class.

Sample output:

<div>
  <label class="error" for="user_email">Email</label>
  <input name="user[email]" size="30" class="error" type="text" id="user_email" value="" />
</div>

Only error message

<%= error_messages_for :order, :header_message => nil, :message => nil %>

Browser view code

<div id=“errorExplanation” class=“errorExplanation”>

  <ul>
    <li>Weight 只有 1000.0</li>
    <li>Volume 只有 10.0</li>
  </ul>
</div>