Enumerable in Rails: index_by and index_with

index_by()

Convert an enumerable to a hash, using the block result as the key and the element as the value.

Source: Enumerable: index_by

index_with(default = INDEX_WITH_DEFAULT)

Convert an enumerable to a hash, using the element as the key and the block result as the value.

Source: Enumerable: index_with

New to me. These seem nice, and a good replacement for some incantations with Hash[].