gistfile1.rb

class Foo
  def self.string_query_accessor(attr, *true_values)
    true_values.each do |true_value|
      class_eval %{
        def #{true_value}?
          send(:#{attr}) == '#{true_value}'
        end
      }, __FILE__, __LINE__
    end
  end
  
  attr_accessor :foo
  string_query_accessor :foo, 'bar', 'baz'
end

f = Foo.new

f.foo = 'bar'
p f.bar?, f.baz?

f.foo = 'baz'
p f.bar?, f.baz?