method

increment_counter

Importance_3
v1.1.6 - Show latest stable - 3 notes - Class: ActiveRecord::Base
increment_counter(counter_name, id) public

Increments the specified counter by one. So DiscussionBoard.increment_counter("post_count", discussion_board_id) would increment the "post_count" counter on the board responding to discussion_board_id. This is used for caching aggregate values, so that they don’t need to be computed every time. Especially important for looping over a collection where each element require a number of aggregate values. Like the DiscussionBoard that needs to list both the number of posts and comments.

Show source
Register or log in to add new notes.
September 30, 2009
2 thanks

See also: ActiveRecord::Base#increment

This is a class-level method. For the instance-level equivalent see: ActiveRecord::Base#increment

item = Item.find(1)
item.foo_count # => 0
Item.increment_counter(:foo_count, 1)
item.foo_count # => 0
item.reload
item.foo_count # => 1
item.increment(:foo_count)
item.foo_count # => 2
March 5, 2012
0 thanks

won't refresh updated_at

This will not cause :updated_at column to refresh, while ActiveRecord::Base#increment! would.

November 5, 2013
0 thanks

The "instance-level equivalent" ActiveRecord::Base#increment is NOT atomic

Typically, you want to increment counters atomically, so the class method ActiveRecord::Base.increment_counter is the right choice.

Also, there is an issue with the increment example below as it does not save automatically:

item = Item.find(1)
item.foo_count # => 0
item.increment(:foo_count)
item.foo_count # => 1
item.reload
item.foo_count # => 0
item.increment(:foo_count)
item.save
item.reload
item.foo_count # => 1