hash_array_access.rb

# Allows access to deep hashes by passing an array of keys, which will be used
# in a serial chain of hash key lookups. For example, the array:

# [:one, :two, :three]

# Would translate to the key structure:

# hash[:one][:two][:three]

# Usage:

# {one: {two: {three: 'bar'} } }.ary_access [:one, :two, :three] # => 'bar'

# By passing two arguments, you can assign a value to the specified hash key and
# get the value in return:

# {one: {two: {three: 'bar'} } }.ary_access [:one, :two, :three], 'baz' # => 'baz'
module HashArrayAccess
  def ary_access(keys, value=nil)
    keys = keys.dup
    if keys.size > 1
      hash = self[keys.shift]
      hash.ary_access(keys, value)
    else
      if value
        self[keys.shift] = value
      else
        self[keys.shift]
      end
    end
  end
end

usage.rb

# Include HashArrayAccess in Hash to add the ary_access method
class Hash; include HashArrayAccess; end

def sep; puts "\n"; end

hash = {one: {two: {three: 'bar'} } }

keys = [:one, :two, :three]

puts "Hash, keys:"
puts "#{hash.inspect}, #{keys.inspect}"
puts "hash.ary_access keys"
p hash.ary_access keys
sep

puts "Hash, keys:"
puts "#{hash.inspect}, #{keys.inspect}"
puts "p hash.ary_access keys, \"baz\""
p hash.ary_access keys, "baz"
sep

puts "Hash, keys:"
puts "#{hash.inspect}, #{keys.inspect}"
puts "p hash.ary_access keys"
p hash.ary_access keys
sep

puts "Hash:"
p hash