From: "rosenfeld (Rodrigo Rosenfeld Rosas)" <rr.rosas@...>
Date: 2012-11-08T06:04:53+09:00
Subject: [ruby-core:49070] [ruby-trunk - Feature #7297] map_to alias for each_with_object


Issue #7297 has been updated by rosenfeld (Rodrigo Rosenfeld Rosas).


I like the "associate" name but I prefer the implementation to be like the hash_map described above. I have lots of situations where the element of the Enumerable is not the key of the resulting hash. Your suggestions sounds inefficient to me for this case:

collection.map { |v| [v.attribute_id, v.some_value] }.associate

I guess this will always perform worse than:

collection.associate{|h, v| h[v.attribute_id] = v.some_value }
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Feature #7297: map_to alias for each_with_object
https://bugs.ruby-lang.org/issues/7297#change-32596

Author: nathan.f77 (Nathan Broadbent)
Status: Rejected
Priority: Normal
Assignee: 
Category: lib
Target version: 2.0.0


I would love to have a shorter alias for 'each_with_object', and would like to propose 'map_to'. Here are my arguments:

* It reads logically and clearly:

[1, 2, 3].map_to({}) {|i, hash| hash[i] = i ** 2 }
#=> {1 => 1, 2 => 4, 3 => 9}

* Rubyists are already using 'map' to build and return an array, so it should be obvious that 'map_to(object)' can be used to build and return an object.

* Given that 'each' and 'each_with_index' return the original array, I feel that the 'each_with_object' method name is slightly counterintuitive. 'map_to' might not be 100% semantically correct, but it's obvious that it will return something other than the original array.

* Many people (myself included) were using inject({}) {|hash, el| ... ; hash } instead of 'each_with_object', partly because of ignorance, but also because 'each_with_object' is so long. 'map_to' is the same length as inject, and means that you don't have to return the object at the end of the block.

* Only a single line of code is needed to implement the alias.


Best,
Nathan


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