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2

I want to make a Ruby nested hash table class to avoid repeating ugly code and to keep my programs as true to the OOP paradigm as I can. Are there any ways to make this class definition smaller and/or simpler?

To clarify, the class essentially creates an arbitrarily-deep hash table. For example, if you had a NestedHash object called foo, you could write foo[:a][:b][:c] = 1.

class NestedHash
  include Enumerable

  def initialize
    @outer = Hash.new { |hash, key| hash[key] = Hash.new(&hash.default_proc) }
  end

  def keys
    @outer.keys
  end

  def values
    @outer.values
  end

  def [](key)
    @outer[key]
  end

  def []=(key, value)
    @outer[key] = value
  end

  def each
    @outer.each { |key, value| yield(key, value) }
  end
end
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up vote 2 down vote accepted

So really, the meat of your whole program is in the single line of the constructor. The rest of it is just forwarding methods to @outer. So we should do that explicitly:

require 'forwardable'

class NestedHash
  extend Forwardable
  include Enumerable

  def_delegators :@outer, :[], :[]=, :keys, :values, :each

  def initialize
    @outer = Hash.new { |hash, key| hash[key] = Hash.new(&hash.default_proc) }
  end

end

h = NestedHash.new
h[:a][:b] = 99
p h[:a][:b]    #=> 99

Keep in mind that you can get the same effect also by just doing:

module NestedHash
  def self.create
    Hash.new { |hash, key| hash[key] = Hash.new(&hash.default_proc) }
  end
end

and use it like:

h = NestedHash.create
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