Method: ActiveRecord::CounterCache::ClassMethods#decrement_counter

Defined in:
activerecord/lib/active_record/counter_cache.rb

#decrement_counter(counter_name, id, by: 1, touch: nil) ⇒ Object

Decrement a numeric field by one, via a direct SQL update.

This works the same as #increment_counter but reduces the column value by 1 instead of increasing it.

Parameters

  • counter_name - The name of the field that should be decremented.

  • id - The id of the object that should be decremented or an array of ids.

  • :by - The amount by which to decrement the value. Defaults to 1.

  • :touch - Touch timestamp columns when updating. Pass true to touch updated_at and/or updated_on. Pass a symbol to touch that column or an array of symbols to touch just those ones.

Examples

# Decrement the posts_count column for the record with an id of 5
DiscussionBoard.decrement_counter(:posts_count, 5)

# Decrement the posts_count column for the record with an id of 5
by a specific amount.
DiscussionBoard.decrement_counter(:posts_count, 5, by: 3)

# Decrement the posts_count column for the record with an id of 5
# and update the updated_at value.
DiscussionBoard.decrement_counter(:posts_count, 5, touch: true)



203
204
205
 
# File 'activerecord/lib/active_record/counter_cache.rb', line 203

def decrement_counter(counter_name, id, by: 1, touch: nil)
  update_counters(id, counter_name => -by, touch: touch)
end