Add methods for Hash to deep_stringify_keys or deep_symbolize_keys

core_extensions.rb

#Load in rails via:
# config/initializers/core_extensions.rb
#Forcibly require our core extensions after rails has loaded

Dir.glob(Rails.root.join('lib', 'core_ext', '*.rb')).each { |extension| require extension }

hash.rb

#lib/core_ext/hash.rb
class Hash

  def deep_symbolize_keys
    dup.deep_symbolize_keys!
  end

  def deep_stringify_keys
    dup.deep_stringify_keys!
  end

  def deep_symbolize_keys!
    deep_change_keys!(:to_sym)
  end

  def deep_stringify_keys!
    deep_change_keys!(:to_s)
  end

  def deep_change_keys!(change_method = :to_s)
    self.keys.each do |k|
      new_key = k.send(change_method)
      current_value = self.delete(k)
      self[new_key] = current_value.is_a?(Hash) ? current_value.dup.deep_change_keys!(change_method) : current_value
    end
    self
  end
end

hash_spec.rb

require 'spec_helper'

describe Hash do

  before(:all) do

    @example_deep_hash = {
      :sym_key => {
        :level_1 => {
          :level_2 => {
            :level_3 => 'Some Value'
          }
        }
      },
      'str_key' => {
        'level_1' => {
          'level_2' => {
            'level_3' => 'Some Value'
          }
        }
      }
    }

    @example_shallow_hash = {
      :simple_key => 'simple value',
      'simpleStringKey' => 'simple second value'
    }
  end

  describe "#deep_symbolize_keys" do

    before(:all) do
      @expected_deep_hash = {
        :sym_key => {
          :level_1 => {
            :level_2 => {
              :level_3 => 'Some Value'
            }
          }
        },
         :str_key => {
          :level_1 => {
            :level_2 => {
              :level_3 => 'Some Value'
            }
          }
        }
      }

      @expected_shallow_hash = {
        :simple_key => 'simple value',
        :simpleStringKey => 'simple second value'
      }
    end

    it 'should be able to run without destructive update' do
      @example_deep_hash.deep_symbolize_keys.should == @expected_deep_hash
      @example_deep_hash.should == @example_deep_hash
    end

    it 'should convert deep hashes to symbolized keys' do
      test_hash = @example_deep_hash.dup
      test_hash.deep_symbolize_keys!
      test_hash.should == @expected_deep_hash
    end

    it 'should convert simple hashes to symbolized keys' do
      test_hash = @example_shallow_hash.dup
      test_hash.deep_symbolize_keys!
      test_hash.should == @expected_shallow_hash
    end

  end

  describe "#deep_stringify_keys" do

    before(:all) do
      @expected_deep_hash = {
        'sym_key' => {
          'level_1' => {
            'level_2' => {
              'level_3' => 'Some Value'
            }
          }
        },
         'str_key' => {
          'level_1' => {
            'level_2' => {
              'level_3' => 'Some Value'
            }
          }
        }
      }

      @expected_shallow_hash = {
        'simple_key' => 'simple value',
        'simpleStringKey' => 'simple second value'
      }
    end

    it 'should be able to run without destructive update' do
      @example_deep_hash.deep_stringify_keys.should == @expected_deep_hash
      @example_deep_hash.should == @example_deep_hash
    end

    it 'should convert deep hashes to string keys' do
      test_hash = @example_deep_hash.dup
      test_hash.deep_stringify_keys!
      test_hash.should == @expected_deep_hash
    end

    it 'should convert simple hashes to string keys' do
      test_hash = @example_shallow_hash.dup
      test_hash.deep_stringify_keys!
      test_hash.should == @expected_shallow_hash
    end
  end

end