From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS4713 221.184.0.0/13 X-Spam-Status: No, score=-4.1 required=3.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_PASS shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from neon.ruby-lang.org (neon.ruby-lang.org [221.186.184.75]) by dcvr.yhbt.net (Postfix) with ESMTP id 9243C1F463 for ; Fri, 20 Dec 2019 07:28:36 +0000 (UTC) Received: from neon.ruby-lang.org (localhost [IPv6:::1]) by neon.ruby-lang.org (Postfix) with ESMTP id 05714120B6E; Fri, 20 Dec 2019 16:28:24 +0900 (JST) Received: from xtrwkhkc.outbound-mail.sendgrid.net (xtrwkhkc.outbound-mail.sendgrid.net [167.89.16.28]) by neon.ruby-lang.org (Postfix) with ESMTPS id F1883120B6A for ; Fri, 20 Dec 2019 16:28:21 +0900 (JST) Received: by filterdrecv-p3mdw1-56c97568b5-bbmbb with SMTP id filterdrecv-p3mdw1-56c97568b5-bbmbb-18-5DFC781C-12 2019-12-20 07:28:28.236248503 +0000 UTC m=+283516.872819444 Received: from herokuapp.com (unknown [3.83.106.33]) by ismtpd0029p1mdw1.sendgrid.net (SG) with ESMTP id AETzjJS1RH6nTvDjPd2pgg for ; Fri, 20 Dec 2019 07:28:28.155 +0000 (UTC) Date: Fri, 20 Dec 2019 07:28:28 +0000 (UTC) From: knu@ruby-lang.org Message-ID: References: Mime-Version: 1.0 X-Redmine-MailingListIntegration-Message-Ids: 72029 X-Redmine-Project: ruby-trunk X-Redmine-Issue-Id: 16274 X-Redmine-Issue-Author: sawa X-Redmine-Sender: knu X-Mailer: Redmine X-Redmine-Host: bugs.ruby-lang.org X-Redmine-Site: Ruby Issue Tracking System X-Auto-Response-Suppress: All Auto-Submitted: auto-generated X-SG-EID: =?us-ascii?Q?hDsQvKErLSJ7pAc+tDc0a0gaAYeRBj5seyyxgbnjKEkRchdBo4YPkYVUM6KHz0?= =?us-ascii?Q?57hE9YYCl1skVX8qnZJtG8w5cPpWYb2q1ivtSbe?= =?us-ascii?Q?o91nRWohoL1tRcBDAGnLTUVCvzbrJc0VIomPzM2?= =?us-ascii?Q?9h+0cGlAZXX0U4oaut01zcHhhZmY1BwrJ+nflEk?= =?us-ascii?Q?oGyx6U8vG47HttBWiK+Yeqs9io9y1ZV+yh0ItLm?= =?us-ascii?Q?Gk9xNUsut3estQVUw=3D?= To: ruby-core@ruby-lang.org X-ML-Name: ruby-core X-Mail-Count: 96369 Subject: [ruby-core:96369] [Ruby master Feature#16274] Transform hash keys by a hash X-BeenThere: ruby-core@ruby-lang.org X-Mailman-Version: 2.1.15 Precedence: list Reply-To: Ruby developers List-Id: Ruby developers List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: ruby-core-bounces@ruby-lang.org Sender: "ruby-core" Issue #16274 has been updated by knu (Akinori MUSHA). Which does `hash1.transform_keys(hash2)` iterate over, hash1's keys or hash2's keys? ---------------------------------------- Feature #16274: Transform hash keys by a hash https://bugs.ruby-lang.org/issues/16274#change-83283 * Author: sawa (Tsuyoshi Sawada) * Status: Open * Priority: Normal * Assignee: * Target version: ---------------------------------------- We have `Hash#transform_keys` and its bang version to change the keys of a hash, but that requires passing a block, which assumes that the mapping from the old keys to the new keys follows some rule. But in reality, we frequently want to change the keys where it is difficult to provide a rule. For example, suppose we have: ``` hash = {created: 2019-10-23 17:54:46 +0900, updated: 2019-10-23 17:59:18 +0900, author: "foo"} ``` and want to achieve: ``` {created_at: 2019-10-23 17:54:46 +0900, update_time: 2019-10-23 17:59:18 +0900, author: "foo"} ``` I request an option to change the keys of a hash not by giving a block, but by passing a hash. I came up with two options. ### 1. Argument for `Hash#transform_keys` and its bang version Allow `Hash#transform_keys` to optionally take a hash argument instead of a block. ``` hash.transform_keys({created: :created_at, updated: :update_time}) # => {created_at: 2019-10-23 17:54:46 +0900, update_time: 2019-10-23 17:59:18 +0900, author: "foo"} ``` ### 2. Argument for `Hash#slice` and the counterparts in other classes Since `Hash#slice` is often the first step of modifying a hash into some other hash form, it makes sense to let it take an optional hash argument. ``` hash.slice(:created, :author, transform_keys: {created: :created_at}) # => {created_at: 2019-10-23 17:54:46 +0900, author: "foo"} ``` With option 1, it could make sense to even allow a hash argument and a block simultaneously: ``` hash.transform_keys({created: :created_at, updated: :update_time}, &:to_s) # => {"created_at" => 2019-10-23 17:54:46 +0900, "update_time" => 2019-10-23 17:59:18 +0900, "author" => "foo"} ``` -- https://bugs.ruby-lang.org/