Serialization issue with Rails and jsonb

serialization.rb

#!/usr/bin/env ruby

gem 'activerecord'
gem 'minitest'
require 'active_record'
require 'minitest/autorun'

ActiveRecord::Base.establish_connection(
  adapter: 'postgresql',
  database: 'playground'
)

ActiveRecord::Schema.define do
  create_table :items, :force => true do |t|
    t.jsonb :data, null: false, default: '[]'
  end
end

class Item < ActiveRecord::Base
  serialize :data, JSON
end

class SerializationTest < Minitest::Test

  def item
    @item ||= Item.new
  end

  def test_item_serializes
    assert_equal [], item.data
  end

end

# TypeError: no implicit conversion of Array into String

So, the nice thing is that without using the serialize macro, we get deserialized data from the adapter. The bad thing is that this breaks typical serialize behavior in that the data isn't known to be deserialized yet, so it gets passed to the load method of a defined serializer, if we use one. Easy enough to work around, but definitely unexpected.

https://gist.github.com/ernie/33f75f2294885b9806f9#file-serialization-rb-L15 This shouldn't be a string, you should give it a valid ruby value.

https://gist.github.com/ernie/33f75f2294885b9806f9#file-serialization-rb-L20 You don't need this.

Yeah, the semantics of the old serialize macro are really wonky. The rough plan is to soft deprecate it for complex cases in favor of the attributes API. In the case, you don't need to use serialize at all though, the attributes type handles it properly.

For those who might see this later: I know I don't need serialize in this simple case. In the real case, I'm serializing/deserializing to an object in my domain model. It's probably worth noting to folks that they will get the deserialized hash/array in their load method if their column type is json/jsonb.

It makes sense, if you think in terms of what the adapter delivers being the "serialized" data, but it's not entirely intuitive, either.