sonic-pi

ActiveSupport::HashWithIndifferentAccess#update

Updates the receiver in-place, merging in the hash passed as argument:

  hash_1 = ActiveSupport::HashWithIndifferentAccess.new
  hash_1[:key] = 'value'

  hash_2 = ActiveSupport::HashWithIndifferentAccess.new
  hash_2[:key] = 'New Value!'

  hash_1.update(hash_2) # => {"key"=>"New Value!"}

The argument can be either an
<tt>ActiveSupport::HashWithIndifferentAccess</tt> or a regular +Hash+.
In either case the merge respects the semantics of indifferent access.

If the argument is a regular hash with keys +:key+ and +"key"+ only one
of the values end up in the receiver, but which one is unspecified.

When given a block, the value for duplicated keys will be determined
by the result of invoking the block with the duplicated key, the value
in the receiver, and the value in +other_hash+. The rules for duplicated
keys follow the semantics of indifferent access:

  hash_1[:key] = 10
  hash_2['key'] = 12
  hash_1.update(hash_2) { |key, old, new| old + new } # => {"key"=>22}

Source | Google | Stack overflow