Ruby’s Hash Vs ActiveSupport’s HashWithIndifferentAccess

The Hash class in Ruby’s core library retrieves values by doing a standard == comparison on the keys. This means that a value stored for a Symbol key (e.g. :some_value) cannot be retrieved using the equivalent String (e.g. ‘some_value’). 

On the other hand, class HashWithIndifferentAccess is inherited from ruby "Hash" & a special behavior is added in it. HashWithIndifferentAccess treats Symbol keys and String keys as equivalent so that the following would work:

h = HashWithIndifferentAccess.new
h[:my_value] = 'foo'
h['my_value'] #=> will return "foo"

Lets discuss this in more details:

Below is the simple example that will show you difference between simple ruby hash & a "ActiveSupport::HashWithIndifferentAccess"

Ruby Hash

$ irb
  > hash = {a: 1, b:2}
    => {:a=>1, :b=>2} 
  > hash[:a]
    => 1 
  > hash["a"]
    => nil 

ActiveSupport::HashWithIndifferentAccess

>> hash = ActiveSupport::HashWithIndifferentAccess.new(a: 1, b:2)
 => {"a"=>1, "b"=>2} 
> hash[:a]
 => 1 
> hash["a"]
 => 1