Question

Hey! Maybe I am getting the idea of a subclass wrong, but I have a Person model and it has an attrib called “age” so

Person.first.age #=> '20'

Now I want to have a model that’s basically persons 55 or older so I know I can have a class like this:
class Senior < Person
end

But how can I “pre-filter” the Senior class so that every object belonging to that class has age >= 55?

Senior.first.age #=> 56

UPDATE1:
So say I have Company has_many people, and Person belongs_to Company, so
Company.first.people #=> [“Jack”, “Kate”]

If Jack’s age is > 55, will it work then:
Company.first.seniors #=> “jack”

Or

Company.first.people.senior(s) #=> “jack”?

I know that named_scope might be what I want, but I also notice that named_scope seems to be a method on the Class variable Person. Not its instances, which does make sense to me. — So if I were to devise such a convenience filter for a collection of activerecord models (objects of the same class), how do I go about it? I am guessing I’d have to use a “detect” for such an array, but where will this go inside the Model’s definition?

Update 2
I am quite sure I haven’t been clear, so example
Want: first company’s 55 or older people
Company.first.people.detect{|p| p.age > 54}

I know this isn’t very long, but my conditions will go farther than just > 54 and it becomes clumsy to do this detect each time.

Thanks!

Answer 1

You can use named scopes

class Person < ActiveRecord::Base
  named_scope :seniors, :conditions => ['age >= ?', 55]
end

Person.seniors.first.age #=> 83