error message of a child object

class TranslationKey < ActiveRecord::Base
  has_many :key_values
  has_many :translation_values, :through => :key_values
  validates_uniqueness_of :name, :message => "already exist in another

class TranslationValue < ActiveRecord::Base
  has_many :key_values
  has_many :translation_keys, :through => :key_values
  has_many :languages
  validates_presence_of :text, :message => "can't be empty"

in my update action of Key, if the key has non-valid value object I
see this error message:
"Translation values is invalid"

why don't I see: "already exist in another key" instead?

Have a look at this thread from last week, which is the same question.

thanks, looking into this thread.