Lance Pollard Lance Pollard - 3 months ago 16
Ruby Question

Fastest/One-liner way to list attr_accessors in Ruby?

What's the shortest, one-liner way to list all methods defined with

attr_accessor
? I would like to make it so, if I have a class
MyBaseClass
, anything that extends that, I can get the
attr_accessor
's defined in the subclasses. Something like this:

class MyBaseClass < Hash
def attributes
# ??
end
end

class SubClass < MyBaseClass
attr_accessor :id, :title, :body
end

puts SubClass.new.attributes.inspect #=> [id, title, body]


What about to display just the
attr_reader
and
attr_writer
definitions?

Answer

There is no way (one-liner or otherwise) to list all methods defined by attr_accessor and only methods defined by attr_accessor without defining your own attr_accessor.

Here's a solution that overrides attr_accessor in MyBaseClass to remember which methods have been created using attr_accessor:

class MyBaseClass
  def self.attr_accessor(*vars)
    @attributes ||= []
    @attributes.concat vars
    super(*vars)
  end

  def self.attributes
    @attributes
  end

  def attributes
    self.class.attributes
  end
end

class SubClass < MyBaseClass
  attr_accessor :id, :title, :body
end

SubClass.new.attributes.inspect #=> [:id, :title, :body]
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