nested_object_from_hash.rb

class Hash
  def self.to_ostruct(nested_hash_object)
    require 'json'
    require 'ostruct'

    JSON.parse(nested_hash_object.to_json, object_class: OpenStruct)
  end

  def to_ostruct
    self.class.to_ostruct(self)
  end
end

class OpenStruct
  def self.from_nested_hash(nested_hash_object)
    Hash.to_ostruct(nested_hash_object)
  end
end

nested_hash_object = { field: { nested_field: 'value of nested field' } }

Hash.to_ostruct(nested_hash_object) == nested_hash_object.to_ostruct
Hash.to_ostruct(nested_hash_object) == OpenStruct.from_nested_hash(nested_hash_object)

describe 'transforming hash to ostruct' do
  specify 'transforms a nested hash object into a nested ostruct object' do
    ostruct = { field: 'value of field' }.to_ostruct
    expect(ostruct.field).to eq('value of field')

    ostruct = { field: { nested_field: 'value of nested field' } }.to_ostruct
    expect(ostruct.field.nested_field).to eq('value of nested field')
  end

  specify do
    ostruct = OpenStruct.from_nested_hash({ field: 'value of field' })
    expect(ostruct.field).to eq('value of field')

    ostruct = OpenStruct.from_nested_hash({ field: { nested_field: 'value of nested field' } })
    expect(ostruct.field.nested_field).to eq('value of nested field')
  end
end