Rails's ActiveRecord can use a dymatic way to finder
Like this model class in rails:
class Article < ActiveRecord::Base attr_accessible :body, :excerpt, :location, :published_at, :title validates :title, :presence => true validates :body, :presence => true end
It don't have much query function, but you can use query function like:
Article.find_by_title('Hello')
=>; #<;article id:1,="" title:="" "hello",="" ...="">;
It because it use Ruby’s method_missing functionality to automatically create methods that don’t exist until runtime. Using dynamic finders, you can include the attribute you’re looking for directly in the method name.
There are several variations of dynamic finders, which are summarized in the Table:
| Finder | Example |
|---|---|
| find_by_*(cond) | find_by_title('Hello') #=>; Article |
| find_all_by_*(cond) | find_all_by_title('Hello') #=>; Array |
| find_by_*_and_*(cond1, cond2) | find_by_title_and_published_on('Hello', '2012-03-12') #=>;Articlelike creating a record. You can update attributes one at a time and then save the result, or you can update attributes in one fell swoop. When you update a record, a SQL UPDATE statement is constructed behind the scenes. First, you use a find operation to retrieve the record you |
| find_all_by_*_and_*(cond1, cond2) | find_all_by_title_and_published_on('Hello', '2012-03-12') #=>;Array |
Amazing...