Crystal - How to recursively change Hash values and save each change to new Hash

Question

using this Hash object

{"foo" => {"bar" => 1, "baz" => 2}, "bla" => [1,2,3]}

I want to produce this array of Hash objects

[
  {"foo" => "*", "bla" => [1,2,3]},
  {"foo" => {"bar" => "*", "baz" => 2}, "bla" => [1,2,3]},
  {"foo" => {"bar" => "1", "baz" => "*"}, "bla" => [1,2,3]},
  {"foo" => {"bar" => "*", "baz" => 2}, "bla" => "*"}, 
]

Where I basically went over each key and changed its value to "*" while preserving the overall structure of the hash and saved the new hash produced in some array.

I have tried many ideas, but most just wont work as I can guess the Array type before, I only know this hash is produced by JSON.parse and then changed into Hash(String, JSON::Any)

My current try at it

hash = {"bar" => {"and" => "2", "br" => "1"}}
arr = [hash, {"bar" => "1"}]
arr.delete(arr.last)
arr.delete(hash)

def changer(hash, arr, original = nil)
  original = hash.dup
  hash.each do |k, v|
    if v.is_a?(Hash)
       changer(v, arr, hash)
    elsif v.is_a?(Array)
      v.each do |a|
        if a.is_a?(Hash)
            changer(a, arr, hash)
        end  
        end
  elsif v.is_a?(String) && original.is_a?(Hash(String, String))
      original[k.to_s] = "*"
      arr << original
    end
  end
end

Your example code in your "try at it" section has nothing but Strings in your hash, but your stated problem has Int values as well. Do you have a well defined schema for your JSON? — voxobscuro, Feb 14 '18 at 13:24
FWIW, [Ruby](https://carc.in/#/r/3l30) vs [Crystal](https://carc.in/#/r/3l32) compilation error. — Oleh Prypin, Feb 14 '18 at 17:35

score 6 · Accepted Answer · edited Jun 18 '18 at 19:08

Crystal v0.25.0 implements JSON::Any and YAML::Any without recursive aliases. With that change:

require "json"

hash = JSON.parse(%(
  {"foo": {"bar": 1, "baz": 2}, "bla": [1,2,3]}
))

def changer(any : JSON::Any)
  result = [JSON::Any.new("*")]
  if (hash = any.as_h?)
    hash.each do |key, value|
      changer(value).each do |s|
        result << JSON::Any.new(hash.merge({key => s}))
      end
    end
  end
  result
end

puts changer(hash).join("\n")

*
{"foo" => "*", "bla" => [1_i64, 2_i64, 3_i64]}
{"foo" => {"bar" => "*", "baz" => 2_i64}, "bla" => [1_i64, 2_i64, 3_i64]}
{"foo" => {"bar" => 1_i64, "baz" => "*"}, "bla" => [1_i64, 2_i64, 3_i64]}
{"foo" => {"bar" => 1_i64, "baz" => 2_i64}, "bla" => "*"}

Crystal - How to recursively change Hash values and save each change to new Hash

1 Answers1