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Comment by effbott | Hacker News Reader

Ruby really is a great language. The author just posted a poor example that is frankly NOT idiomatic Ruby. The proper way to create a getter and setter method on an instance variable is like so:

  class Person
    attr_accessor :sanity

    def initialize
      @sanity = 50
    end
  end

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All the attr_* class methods do is define precisely the instance methods the author wrote by hand. Indeed, if attr_reader, attr_writer, and attr_accessor weren't part of Ruby's Module class you could write them yourself, like so: https://gist.github.com/jfarmer/6b4deeb8bcfbe030f876

If using an "eval" method seems smelly to you, you can achieve the same result in pure Ruby using define_method, instance_exec, and instance_variable_get. There are good practical reasons to use module_eval, though.

Regardless, I think the author's point was more that there's nothing "special" about getters and setters in Ruby. They're just plain ol' methods. As a class of methods we write them often enough that we've also defined a higher-order method that takes an instance variable name as input and dynamically defines those getters and setters on the underlying object.

We wouldn't "lose" anything by not having attr_reader and friends, though. Our code would just be slightly more verbose.

>Regardless, I think the author's point was more that there's nothing "special" about getters and setters in Ruby. They're just plain ol' methods.

Ah, that's a good point. That seems to be a more accurate interpretation of what the author was trying to express.

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