How to deep_transform_values with keys in Ruby?

Question

Active Support's deep_transform_values recursively transforms all values of a hash. However, is there a similar method that would allow to access the keys of values while transforming?

I'd like to be able to do the following:

keys_not_to_transform = ['id', 'count']

response = { result: 'ok', errors: [], data: { id: '123', price: '100.0', quotes: ['1.0', '2.0'] }, count: 10 }
response.deep_transform_values! do |key, value|
  # Use value's key to help decide what to do
  return value if keys_not_to_transform.any? key.to_s

  s = value.to_s
  if s.present? && /\A[+-]?\d+(\.\d+)?\z/.match?(s)
    return BigDecimal(s)
  else
    value
  end
end

#Expected result 
# =>{:result=>"ok", :errors=>[], :data=>{:id=>"123", :price=>0.1e3, :quotes=>[0.1e1, 0.2e1]}, :count=>10}

Note that we are not interested in transforming the key itself, just having it on hand while transforming the corresponding values.

Answer 1

You could use Hash#deep_merge! (provided by ActiveSupport) like so:

keys_not_to_transform = ['id', 'count']

transform_value = lambda do |value|
    s = value.to_s
    if s.present? && /\A[+-]?\d+(\.\d+)?\z/.match?(s)
      BigDecimal(s)
    else
      value
    end
end

transform = Proc.new do |key,value|
  if keys_not_to_transform.include? key.to_s
    value
  elsif value.is_a?(Array)
    value.map! do |v| 
      v.is_a?(Hash) ? v.deep_merge!(v,&transform) : transform_value.(v)
    end 
  else   
    transform_value.(value)
  end  
end

response = { result: 'ok', errors: [], data: { id: '123', price: '100.0', quotes: ['1.0', '2.0'], other: [{id: '124', price: '17.0'}] }, count: 10 }

response.deep_merge!(response, &transform)

This outputs:

#=>{:result=>"ok", :errors=>[], :data=>{:id=>"123", :price=>0.1e3, :quotes=>[0.1e1, 0.2e1], :other=>[{:id=>"124", :price=>0.17e2}]}, :count=>10}