Indifferent Access in Ruby Hashes (with ActiveSupport)

04 Sep 2015 I kept seeing this “Hash with indifferent access” in open source projects, but never knew quite what it was. Turns out it’s something I use in Rails all of the time without knowing, particularly in dealing with params. It allows me to access values in a hash using either string or symbolized keys.

For example:

params['name'] == params[:name]
# => true

However, a normal Hash in Ruby does not allow this:

hash = { 'name' => 'Fred' }
hash['name']
# => 'Fred'
hash[:name]
# => nil
hash['name'] == hash[:name]
# => false

We can fix this by making this into a hash with indifferent access:

new_hash = hash.with_indifferent_access
new_hash['name'] == new_hash[:name]
# => true

The hash can also be defined/initialized with indifferent access, either by calling that method on the initial hash assignment, or by creating it using ActiveSupport (which is what the with_indifferent_access method does under the hood anyway):

hash = ActiveSupport::HashWithIndifferentAccess.new(name: 'Fred')
hash['name'] == hash[:name]
# => true

Note: When working in straight Ruby, this will not work as it’s using ActiveSupport. One would likely need to run gem install active_support and require it properly.

Source: apidock and RoR api