Form Field Errors Rails 4

_form.slim

= error_message_for(:resource, :field_name, :prepend_text => '')

application_helper.rb

module ApplicationHelper

 # Error messages for the specific form field
  def error_message_for(resource, field, options = {:prepend_text => false})

    error_message = resource.errors[field]

    # If the error messages are not empty put the error messages 
    # and the prepended text unless it's empty then put the field name.
    
    unless error_message.empty?
      "#{options[:prepend_text] || field.to_s.capitalize} #{error_message.to_s}".delete! '[]""'
    end

  end

end