module ToBoolean
  def to_bool
    return true if self == true || self.to_s.strip =~ /^(true|t|yes|y|1)$/i
    return false
  end
end

class NilClass; include ToBoolean; end
class TrueClass; include ToBoolean; end
class FalseClass; include ToBoolean; end
class Numeric; include ToBoolean; end
class String; include ToBoolean; end

injects .to_bool instance method into NilClass, TrueClass, FalseClass, Numeric & String

Ruby To Boolean module

Ruby