// description of your code here
How to manually add errors to the model
Should probably be done as part of the validate callback

self.errors.add :field_name, "isn't as it should be"

I haven’t been able to find anything built into Rails to present errors from model validation when a request is sent via AJAX.

So I came up with this handly little hack, which I’ve put in my application.rb file.

def render_javascript_alert_for_errors_on(object)
  errors = object.errors.full_messages
  alert_text = errors.collect { |error| '-' + error }.join("\n")
  render :update do |page|
    page.alert alert_text
  end
end

This takes the object and displays a nicely-formatted version of all the errors on that object, taking advantage of inline RJS to render the javascript to create an alert().

It works perfectly, but it still feels a little “hacky” to me. Any better ideas?

Перегрузка ошибок

def error_messages_for(object_name, options = {})
        options = options.symbolize_keys
        object = instance_variable_get("@#{object_name}")
        if object && !object.errors.empty?
          content_tag("div",
            content_tag(
              options[:header_tag] || "h2",
              "Из-за #{object.errors.count} #{object.errors.count.items("ошибки", "ошибок", "ошибок")}  #{object_name.ru_name} не будет сохранена"
            ) +
            content_tag("p", "Следующие поля заполнены неверно:") +
            content_tag("ul", object.errors.full_messages.collect { |msg| content_tag("li", msg) }),
            "id" => options[:id] || "errorExplanation", "class" => options[:class] || "errorExplanation"
          )
        else
          ""
        end
       end