ruby - attr vs attr_accessor

Question

In Ruby there are four different getter and setter methods for instance variables, attr, attr_reader, attr_writer, and attr_accessor. The question is, is in Ruby attr :dilithium, the same as attr_reader :dilithium, and identical to attr_accessor :dilithium if an additional parameter true is passed? That is to say is

class Enterprise
  attr :dilithium, true

identical to

class Enterprise
  attr_accessor :dilithium

Are the two functions attr and attr_accessor more or less redundant?

Answer 1

One difference is that attr_accessor and friends are clearer, and the optional boolean argument to attr is now deprecated. Other than that, and the fact that attr has no documentation, there's no real difference.