STI update

sti_update.rb

module StiUpdate
  def as(type)
    if self.type == type
      self
    else
      klass = type.camelize.constantize
      if klass.nil?
        self
      else
        became = self.becomes!(klass)
        # the only hack here: @errors instance may contain a reference to the source object
        became.instance_variable_set(:@errors, nil)
        became
      end
    end
  end

  def update_as(type, params)
    became = as(type)
    became.update(params)
    became
  end
end
 
# Usage example (e.g. in your controller)
def update
  @post = @post.update_as(post_params[:type] || @post.type, post_params)
  
  if @post.valid?
    ...
  else
    ...
  end
end