Cannot update attributes through = and save - ruby-on-rails

Question

Following is the problem puzzling me:
I have a model Word, and it has an attribute article_count
however, if I use:
w = Word.first
w.article_count = 1
w.save
the the first word's article_count will not change, the log shows:
Word Exists (0.4ms) ...
but I can use
w.update_attributes :article_count => 1
Maybe I misunderstood the function of save, can anyone explain to me?
======================= Update =======================
Here is my article model:
class Article < ActiveRecord::Base
attr_accessible :content, :title, :source, :url
has_many :article_wordships, :dependent => :destroy
has_many :words, :through => :article_wordships
has_many :paragraphs, :dependent => :destroy
alias_attribute :word_count, :article_wordships_count
validates_uniqueness_of :title
end
Here is my code:
Article.select(:title).all.each do |a|
a.title = a.title.gsub(/\A.+?;\s(.+)/, '\1')
a.save
end
And after run the code, nothing changes in the articles.
Here is the console info:
1.9.3p194 :003 > a.save
(0.2ms) BEGIN
Article Exists (0.6ms) SELECT 1 AS one FROM `articles` WHERE (`articles`.`title` = BINARY 'A Shared State of Defeat' AND `articles`.`id` != 178) LIMIT 1
(0.9ms) UPDATE `articles` SET `title` = 'A Shared State of Defeat', `updated_at` = '2012-09-08 02:58:33' WHERE `articles`.`id` = 178
(2.2ms) COMMIT
=> true
Both save and save! return true.
Strangely, SOMETIMES IT WORKS, SOMETIMES IT DOES NOT WORK!
I'm getting mad...

Answer 1

I am not sure what you mean "SOMETIMES IT WORKS, SOMETIMES IT DOES NOT WORK!" It seems to work in the example you give. If by not work you mean it does not always issue updates, it might be that this line does not change the title. ActiveRecord does dirty checking and if the value of title does not change, it will not issue an update.
a.title = a.title.gsub(/\A.+?;\s(.+)/, '\1')