accessor attributes don't return correct values when Jsonb field elements are updated directly

[drkelly58]

I have a simple class as follows:

class Foo < ApplicationRecord jsonb_accessor :data, field1: :string, field2: [:string, default: 'default for field2'], field3: :string end

if I create a new instance of foo, and set foo.field1, & foo.field2. Values get populated into jsonb and are also present via accessor attributes.

But if i set foo['field1'] or data.update({field1:'new', field2:'value'}). Jsonb gets correct values but accessor attributes still have old values.

Once record is persisted & reloaded values are correct, however prior to a reload values remain out of sync. This presents a real problem with callbacks after_save & after_commit as they get out of sync values.

[haffla]

Hi @drkelly58 . Please provide a proper code example that I can run myself. Like this it's hard to understand what you mean.

[drkelly58]

class TestJob < ApplicationRecord
  jsonb_accessor :metadata,
  attribute1: :integer,
  attribute2: :string

  def test
    self.attribute1 = 100
    self.attribute2 = 'just testing'
    puts metadata
    puts "value of attribute1 via accessor: #{ attribute1 }"
    puts "value of attribute1 via square bracket notation: #{ metadata['attribute1'] }"
    metadata['attribute1'] = 105
    puts 'updated attribute1 value using square bracket notation'
    puts "value of attribute1 via accessor: #{ attribute1 }"
    puts "value of attribute1 via square bracket notation: #{ metadata['attribute1'] }"
  end

end

Sample results from console

job = TestJob.new

3.0.3 :048 > job.test {"attribute1"=>100, "attribute2"=>"just testing"} value of attribute1 via accessor: 100 value of attribute1 via square bracket notation: 100 updated attribute1 value using square bracket notation value of attribute1 via accessor: 100 value of attribute1 via square bracket notation: 105

[haffla]

You are right, there is something fishy. I am on it.

[haffla]

OK so I have looked into this. Unfortunately your use case is not supported.

There are some ways to update a value. Either you replace the whole metadata (in your case) hash using instance.metadata = { ... } or you use the generated setters, e.g. instance.attribute1 = 100 or even instance.update(attribute1: 100).

The explanation is that this gem relies on https://api.rubyonrails.org/classes/ActiveRecord/Attributes/ClassMethods.html. For each key in your config (attribute1 and attribute2) it creates a Rails attribute. After an object initializes it goes through the raw JSON hash and uses write_attribute to populate the attributes. The gem also overwrites the method metadata=. Here again it can go through that hash and use write_attribute to make sure the Rails attributes are in sync.

But when you do instance.metadata['attribute1'] = 105 you are updating the hash itself and the gem has no way of knowing about this update. So in this case instance.attribute1 (the Rails attribute) gets out of sync.

[drkelly58]

@haffla Thanks for the explanation, that makes sense