update_counters

A generic "counter updater" implementation, intended primarily to be used by increment_counter and decrement_counter, but which may also be useful on its own. It simply does a direct SQL update for the record with the given ID, altering the given hash of counters by the amount given by the corresponding value:

Options

id The id of the object you wish to update a counter on counters An <a href="/rails/Array">Array</a> of Hashes containing the names of the fields

            to update as keys and the amount to update the field by as
            values

Examples

  # For the Post with id of 5, decrement the comment_count by 1, and
  # increment the action_count by 1
  Post.update_counters 5, :comment_count => -1, :action_count => 1
  # Executes the following SQL:
  # UPDATE posts
  #    SET comment_count = comment_count - 1,
  #        action_count = action_count + 1
  #  WHERE id = 5