gistfile1.rb

# BONUS PARTY GAME - Choose 1 or make your own! Is this DRY gone mad?

# A
  named_scope :leads,   :conditions => ["dancers.lead = ?", true],  :joins => :dancer
  named_scope :follows, :conditions => ["dancers.lead = ?", false], :joins => :dancer

# B
  [
    [:leads,   true], 
    [:follows, false]
  ].each do |role, data|
    named_scope name, :conditions => ["dancers.lead = ?", data], :joins => :dancer
  end

# C
  lambda {|role_conditions|
    named_scope :leads,   role_conditions[true]
    named_scope :follows, role_conditions[false]
  }[lambda {|x| {
    :conditions => ["dancers.lead = ?", x],
    :joins      => :dancer
  }}]

# D
  with(L{|x| {:conditions => ["dancers.lead = ?", x], :joins => :dancer}}) do |f|
    named_scope :leads,   f[true]
    named_scope :follows, f[false]
  end

# E
  named_scope :with_role, lambda { |role| :conditions => ["dancers.lead = ?", role == :lead ? true : false], :joins => :dancer }
# eg.
  Partner.with_role(:lead)
  Partner.with_role(:follow)