Feature #14371: New option "recursive: true" for Hash#transform_keys!

• Status: Rejected
• Assignee: -
• Target version: -

[tagomoris (Satoshi Tagomori)]

Hash#transform_keys! is available when we want to symbolize hash keys.
But in some/many cases (for example, receiver hash object is nested configuration tree loaded from any files), hash object are
nested object, which has hashes or arrays of hashes as values.
It's super useful if we can transform keys of such nested values.

My proposal is Hash#transform_keys!(recursive: true, &:to_sym). Pseudo code is:

def transform_keys!(recursive: false, &block)
  # do original transform_keys! here
  values.each do |v|
    if v.respond_to?(:each)
      v.each{|i| i.transform_keys!(recursive: true, &block) if i.respond_to?(:transform_keys!) }
    else v.respond_to?(:transform_keys!)
      v.transform_keys!(recursive: true, &block)
    end
  end if recursive
end

The most major usage example is: config = MyAwesomeFormat.load(file); config.transform_keys!(recursive: true, &:to_sym).

[naruse (Yui NARUSE)]

• Description updated (diff)

[nobu (Nobuyoshi Nakada)]

• Description updated (diff)

tagomoris (Satoshi TAGOMORI) wrote:

    if v.respond_to?(:each)
    else v.respond_to?(:transform_keys!)

Why prefer each over transform_keys!?
And probably you wanted to write elsif.

[tagomoris (Satoshi Tagomori)]

Why prefer each over transform_keys!?
And probably you wanted to write elsif.

Your points are correct. The ideal pseudo code is here:

def transform_keys!(recursive: false, &block)
  # do original transform_keys! here
  values.each do |v|
    if v.respond_to?(:transform_keys!)
      v.transform_keys!(recursive: true, &block)
    elsif v.respond_to?(:each)
      v.each{|i| i.transform_keys!(recursive: true, &block) if i.respond_to?(:transform_keys!) }
    end
  end if recursive
end

[shevegen (Robert A. Heiler)]

I agree with the proposal.

If it is approved, please do not forget meaningful documentation + perhaps
at the least one short example for using it (I refer to the recursive: true
option; http://ruby-doc.org/core-2.5.0/Hash.html#method-i-transform_keys-21).

[nobu (Nobuyoshi Nakada)]

https://github.com/nobu/ruby/tree/feature/14371-transform_keys-recursive

[matz (Yukihiro Matsumoto)]

I don't think this proposal is a good idea for following reasons:

• transform_keys method to modify value part of Hash
• recursive option to change the behavior this much
• it is much harder to implement transform_keys(recursive:true) (without bang)

I understand the intention behind the proposal. Probably you want to process JSON-like Array-Hash structures. I feel the recent demand to handle those data structures in Ruby. So we might need to add some utility methods in Ruby. I am not sure how yet. Maybe by adding methods to JSON module, or adding them both Array and Hash (like dig).

Matz.

[sakuro (Sakuro OZAWA)]

FYI, ActiveSupport implemented these functionalities as separate methods:

• Hash#deep_transform_keys
• Hash#deep_transform_keys!

[tagomoris (Satoshi Tagomori)]

• Status changed from Open to Rejected

I see. Thank you!