[shared] rails render_invalid method

purpose

provide DRY solution for rendering (or redirecting) from controller on invalid request, such as failed validation on create/update

requirements

- jquery js framework
- notifications helper from my earlier post about custom ajax helper:
http://tech.maysora.com/2010/11/rails-custom-ajax-helper-for-jquery.html

codes

application_controller.rb

# render invalid request to show error message depend on request type
# example:
#   render_invalid "Update failed."
#     ajax: show error notification with message "Update failed."
#     html: simply render text "Update failed."
#   render_invalid "Save failed.", :render => {:action => "new"}
#     ajax: show error notification with message "Save failed."
#     html: render action new with "Save failed." flash message
#   render_invalid "Save failed.", :render => {:action => "new"}, :flash => false
#     same as above but without flash for html
#   render_invalid "You can't do that.", :redirect_to => {:action => "index"}, :flash => false, :status => :unauthorized
#     same as above but redirecting to index instead of rendering new for html
#     and using unauthorized(401) status instead of not_acceptable(406)
#   render_invalid "Update failed.", :object => @user, :fields_wrapping => true
#     ajax: show error notification with addition of object's error messages and wrap error fields with div class fieldWithErrors
#     html: same as ajax minus fields wrapping
def render_invalid message="Error.", options={:flash => true}
  options[:status] ||= :not_acceptable
  message += "
#{options[:object].errors.full_messages.join('
')}
" if options[:object].present?
  respond_to do |format|
    format.js do
      render(:update, :status => options[:status]) do |page|
        page << notification_error(message)
        if options[:object].present? && options[:fields_wrapping]
          page.rjs_clean_error_fields request
          page.rjs_apply_error_fields options[:object], request
        end
      end
    end
    format.html do
      if options[:render].present?
        flash.now[:error] = message if options[:flash]
        render options[:render].try(:merge, {:status => options[:status]}) || {:text => message, :status => options[:status]}
      elsif options[:redirect_to].present?
        flash[:error] = message if options[:flash]
        redirect_to options[:redirect_to]
      else
        render :text => message, :status => options[:status]
      end
    end
  end
end

application_helper.rb (only if you use ajax error fields wrapping)

def rjs_apply_error_fields object, request
  klass_name = object.class.name.underscore
  wrapper = "
"
  object.errors.each do |attr, msg|
    attr = attr.split(".")
    page << "var $fields = $(), $container = $('\##{klass_name}_#{object.id || "new"}');"
    page << "if(!$container.length) $container = $('form[action=\\'#{request.request_uri}\\']');"
    page << "if(!$container.length) $container = $(document);"
    if attr.length > 1
      object.send(attr.first).each_with_index do |x,i|
        page << "$fields = $fields.add('[id^=#{klass_name}_#{attr.first}_attributes][id$=#{attr.last}]:eq(#{i}),label[for^=#{klass_name}_#{attr.first}_attributes][for$=#{attr.last}]:eq(#{i})', $container)" if x.errors.on(attr.last)
      end
    else
      page << "$fields = $('label[for=#{klass_name}_#{attr}],\##{klass_name}_#{attr}', $container);"
    end
    page << "if(!$fields.parent('.fieldWithErrors').length)"
      page << "$fields.wrap('#{wrapper}')"
  end
end

def rjs_clean_error_fields request
  page << "$('.fieldWithErrors.rjs_#{request.request_method}_#{request.request_uri.gsub(/_=\d+($|&)/, "").parameterize} *').unwrap();"
end

usage

users_controller.rb (using non ajax form)

#...

def create
  @user = User.new(params[:user])
  unless @user.save
    render_invalid "Failed to register.", :object => @user, :render => {:action => "new"}
  else
    flash[:info] = "Registration success, please check your email to activate."
    redirect_to login_path
  end
end

#...

users_controller.rb (using ajax form)

#...

def update
  @user = current_user
  unless @user.update_attributes(params[:user])
    render_invalid "Profile update failed.", :object => @user, :fields_wrapping => true
  end
end

#...

and update.js.rjs (for success behavior)

page << notification_info "Profile updated."
page.rjs_clean_error_fields request # used for cleaning error fields wrapping
#... other necessary action ...

additional tips

depending on your site style, it might be a good idea to change the div wrapper in rjs_apply_error_fields helper to span. you can also change rails standard error field wrapper for non-ajax form, see this post