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_acce

Answer 1

If you look at the C code in Ruby 2.3.0, you will see that attr and attr_reader are actually doing the same thing (except for the deprecated code path). They are essentially equivalent functions.

For me, the main differences are:

attr is a bit easier to write down as it's shorter. I like the way it feels in the context of functional/immutable programming too (in those contexts, attr_writer and attr_accessor are irrelevant and thus using attr_reader feels verbose and redundant).

attr with multiple instance variables makes it hard to document, except in very specific situations, e.g.

# The coordinates in WGS84.
attr :x, :y

# The location name.
attr :name

# The popularity of the location.
attr :popularity

It would be harder to document :name and :popularity independently if they were on the same line attr :name, :popularity.

Apart from that it boils down to personal preference. There is in practice no performance difference or any other difference.