class User < ActiveRecord::Base
  named_scope :active, :conditions => {:active => true}
  named_scope :inactive, :conditions => {:active => false}
  named_scope :recent, :conditions => ['created_at > ?', 1.week.ago]
end

# Standard usage
User.active    # same as User.find(:all, :conditions => {:active => true})
User.inactive # same as User.find(:all, :conditions => {:active => false})
User.recent   # same as User.find(:all, :conditions => ['created_at > ?', 1.week.ago])

# They're nest-able too!
User.active.recent
  # same as:
  # User.with_scope(:conditions => {:active => true}) do
  #   User.find(:all, :conditions => ['created_at > ?', 1.week.ago])
  # end

class User < ActiveRecord::Base
  named_scope :registered, lambda { |time_ago| { :conditions => ['created_at > ?', time_ago] }
end

User.registered 7.days.ago # same as User.find(:all, :conditions => ['created_at > ?', 7.days.ago])

class User < ActiveRecord::Base
  named_scope :inactive, :conditions => {:active => false} do
    def activate
      each { |i| i.update_attribute(:active, true) }
    end
  end
end

# Re-activate all inactive users
User.inactive.activate

# Store named scopes
active = User.scoped(:conditions => {:active => true})
recent = User.scoped(:conditions => ['created_at > ?', 7.days.ago)

# Which can be combined
recent_active = recent.active

# And operated upon
recent_active.each { |u| ... }