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Feature #16274

closed

Transform hash keys by a hash

Added by sawa (Tsuyoshi Sawada) almost 3 years ago. Updated almost 2 years ago.

Status:
Closed
Priority:
Normal
Assignee:
-
Target version:
[ruby-core:<unknown>]

Description

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"}
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