As I pointed out here on the WWR Forums when you have a set of static conditions, even if you only use them once, then you should consider using a named_scope to encapsulate those conditions in your model.
So instead of having this in your controller:
app/controller/foos_controller.rb
def inactive
@foos = Foo.all(:conditions => "active is null")
end
You would shift that concept off into your model by using a named scope. So you’d have this instead:
app/models/foo.rb
named_scope :inactive, :conditions => "active is null"
app/controller/foos_controller.rb
def inactive
@foos = Foo.inactive
end
Note that what’s returned from inactive is a proper ActiveRecord collection, so you can call all your AR records on it, eg:
@foos = Foo.inactive.find_all_by_bar(params[:bar])
This is a great way to push the business logic off into your model and refer to it by name (not code) from your controller.
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One of the best uses I’ve come across for named_scope is in dealing with associations:
For example, if you want to find all a user’s inactive foos, you could do:
@foos = @user.foos.inactive
(assuming you had defined that a user class has_many :foos).
The named scope is available anywhere you use the association.
Thanks for that Jared, that really does show the power of this feature.
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