Quick way to build a case statement in SQL using ActiveRecord

case_statement_builder.rb

module CaseStatementBuilder
  class << self
    delegate :connection, :to => ActiveRecord::Base

    def build(lhs, values_hash, default_value)
      when_expressions = values_hash.sort.map do |rhs, value|
        "WHEN #{lhs} = #{connection.quote(rhs)} THEN #{connection.quote(value)}"
      end.join(" ")

      "CASE #{when_expressions} ELSE #{connection.quote(default_value)} END"
    end

    private

    def connection
      ActiveRecord::Base.connection
    end
  end
end