has_many , time now, assocation

Do you know when your code runs?
有時候你時候你會發現你在你下的conditions 有關於時間的, 跑起來有點怪怪的

在development 沒問題, 在production 卻不正常

仔細看會發現時間統統都是static 的了, 因為production 並不會每次都去reload class
<br />class Person < ActiveRecord::Base<br /> has_many :posts<br /> has_many :recent_posts, :class_name => 'Post', :conditions => ["created_at > ?", 1.week.ago]<br /> validates_inclusion_of :birth_date, :in => (20.years.ago..13.years.ago), <br /> :message => "You must be a teenager to signup", :on => :create<br />end<br /><br />class Post < ActiveRecord::Base<br /> named_scope :recent, :conditions => ["created_at > ?", 1.week.ago]<br />end<br />
這時候只要換個寫法<br />#make one with no arguments, just to ensure that the time condition is evaluated whenever the scope is accessed. <br />class Post<br /> named_scope :recent, lambda { {:conditions => 1.week.ago}}<br />end<br /><br />#Active Record will perform that interpolation again at the point where sql is generated<br />class Person < ActiveRecord::Base<br /> has_many :recent_posts, :class_name => 'Post', <br /> :conditions => "created_at > #{1.week.ago.to_s(:db)}"<br />end<br /><br />#Validations can't play any of the clever little games that the other 2 examples can. You'll just have to something like<br />class Person < ActiveRecord::Base<br /> validate_on_create :is_a_teenager<br /><br /> def is_a_teenager<br /> unless birth_date < 13.years.ago && birth_date > 20.years.ago<br /> ...<br /> end<br /> end<br />end<br />