可定制的Rails错误回显

<%= error_message_on "post", "title", 
      :prepend_text => "Title simply ", 
      :append_text => " (or it won't work).", 
      :css_class => "inputError" %> 

8.3 Customizing the Error Messages HTML

By default, form fields with errors are displayed enclosed by a div element with the fieldWithErrors CSS class. However, it’s possible to override that.

The way form fields with errors are treated is defined by ActionView::Base.field_error_proc. This is a Proc that receives two parameters:

    * A string with the HTML tag
    * An instance of ActionView::Helpers::InstanceTag.

Here is a simple example where we change the Rails behaviour to always display the error messages in front of each of the form fields with errors. The error messages will be enclosed by a span element with a validation-error CSS class. There will be no div element enclosing the input element, so we get rid of that red border around the text field. You can use the validation-error CSS class to style it anyway you want.
ActionView::Base.field_error_proc = Proc.new do |html_tag, instance| if instance.error_message.kind_of?(Array) %(#{html_tag}<span class="validation-error">&nbsp; #{instance.error_message.join(',')}</span>) else %(#{html_tag}<span class="validation-error">&nbsp; #{instance.error_message}</span>) end end

This will result in something like the following:

Validation error messages