How to copy the object correctly in this case?

Question

ruby

Type of object to copy

obj = {
id: 1
models: [
    {
      id: 1,
      parent_id: nil
    },
    {
      id: 2,
      parent_id: 1
    },
    {
      id: 3,
      parent_id: 1
    },
    {
      id: 4,
      parent_id: nil
    },
    {
      id: 5,
      parent_id: 4
    },
    {
      id: 6,
      parent_id: 4
    }
  ]
}

There is an object of this type.
praent_idthis is the ID of the same model that has it nil.
When copying it using the methoddup

new_obj = obj.dup
new_obj.save!

obj.models.each do |m|
  new_obj.models << m.dup
end

After copying, parent_idit remains the same.

Correct result

Дата перед копированием.

[
 {
   id: 123,
   parent_id: nil
 },
 {
   id: 456,
   parent_id: 123
 }
]

и после копирования

[
 {
   id: 457,
   parent_id: nil
 },
 {
   id: 458,
   parent_id: 123
 }
]

Правильный результат, должен быть.

[
 {
   id: 457,
   parent_id: nil
 },
 {
   id: 458,
   parent_id: 457
 }
]

How in this case it is correct to distribute parent_idfor models?

Answer 1

If I understand the logic of copying parent_id correctly:

new_obj = {id: new_id, models: []}
prev_model = nil
obj[:models].each do |m|
  new_model = m.dup
  new_model[:parent_id] = prev_model[:id] unless prev_model.nil?
  new_obj[:models] << new_model
  prev_model = new_model
end

 result

{:id=>2,
:models=>
[{:id=>1, :parent_id=>nil},
{:id=>2, :parent_id=>1},
{:id=>3, :parent_id=>2},
{:id=>4, :parent_id=>3},
{:id=>5, :parent_id=>4},
{:id=>6, :parent_id=>5}]}