diff options
| -rw-r--r-- | railties/guides/source/active_record_querying.textile | 34 |
1 files changed, 31 insertions, 3 deletions
diff --git a/railties/guides/source/active_record_querying.textile b/railties/guides/source/active_record_querying.textile index 5cd302f356..eb77a35739 100644 --- a/railties/guides/source/active_record_querying.textile +++ b/railties/guides/source/active_record_querying.textile @@ -768,13 +768,41 @@ h4. Working with times If you're working with dates or times within scopes, due to how they are evaluated, you will need to use a lambda so that the scope is evaluated every time. <ruby> - class Post < ActiveRecord::Base - scope :last_week, lambda { where("created_at < ?", Time.zone.now ) } - end +class Post < ActiveRecord::Base + scope :last_week, lambda { where("created_at < ?", Time.zone.now ) } +end </ruby> Without the +lambda+, this +Time.zone.now+ will only be called once. +h4. Passing in arguments + +When a +lambda+ is used for a +scope+, it can take arguments: + +<ruby> +class Post < ActiveRecord::Base + scope :1_week_before, lambda { |time| where("created_at < ?", time) +end +</ruby> + +This may then be called using this: + +<ruby> +Post.1_week_before(Time.zone.now) +</ruby> + +However, this is just duplicating the functionality that would be provided to you by a class method. + +<ruby> +class Post < ActiveRecord::Base + def self.1_week_before(time) + where("created_at < ?", time) + end +end +</ruby> + +Using a class method is the preferred way to accept arguments for scopes. + h3. Dynamic Finders For every field (also known as an attribute) you define in your table, Active Record provides a finder method. If you have a field called +first_name+ on your +Client+ model for example, you get +find_by_first_name+ and +find_all_by_first_name+ for free from Active Record. If you have a +locked+ field on the +Client+ model, you also get +find_by_locked+ and +find_all_by_locked+ methods. |