search_with_scopes.rb

# Untested, but it should work :)

class Something < ActiveRecord::Base
  # Simpler approach available with this small Rails patch:
  # http://rails.lighthouseapp.com/projects/8994/tickets/1773-allow-returning-nil-from-a-named_scope-lambda
  # 
  # named_scope :with_town_like, lambda { |term|
  #   { :conditions => ['town LIKE ?', term] } unless term.blank?
  # }
  # 
  # named_scope :with_hobby, lambda { |term|
  #   { :conditions => ['hobby = ?', term] } unless term.blank?
  # }
  # 
  # named_scope :age_at_least, lambda { |term|
  #   { :conditions => ['age >= ?', term] } unless term.blank?
  # }

  named_scope :with_town_like, lambda { |term|
    if !term.blank?
      { :conditions => ['town LIKE ?', term] }
    else
      {}
    end
  }

  named_scope :with_hobby, lambda { |term|
    if !term.blank?
      { :conditions => ['hobby = ?', term] }
    else
      {}
    end
  }

  named_scope :age_at_least, lambda { |term|
    if !term.blank?
      { :conditions => ['age >= ?', term] }
    else
      {}
    end
  }

  def search(options = {})
    town_like(options[:town]).
    with_hobby(options[:hobby]).
    age_at_least(options[:age])
  end
end