Serialize/ Deserialize arbitrary Ruby objects to database - ruby

Question

I have a use case to store arbitrary objects (classA or classB or classC) in a column of a database table. Then when I read it, I would like to deserialize it back to the original class (A or B or C) Is it possible to do that?
It seems like I can serialize the object to json, and deserialize it to OpenStruct object. But I am hoping to get the original object so I can send it as a response which can be recognized by my protobuf definition.
[Edit]:
One extra requirement is that my server will have dependency to class A, B, C... but I have no permission to change it. Ideally I want to avoid adding extra initialize or serialize method to it.
The data stored in the database ideally could be readable after someone execute sql query. (not stored in binary format)
What I have tried is to:
Convert the data to hash then to json:
a = classa_obj.to_h.to_json
Store it to db:
active_record_obj.col_a = a
active_record_obj.save
Retrieve the record from db:
query_result = # sql query filter by the id
Covert it the json part back to class A object:
classa_obj = ClassA.new(Json.parse(query_result.col_a))
This seems to work but I am not sure if it apply to some more complicated class structure

Answer 1

Lets say you have a active record class called User and you wanted to store a class A object in a column of a User. Then you need to define that column as json type and store the data in database as hash. When you want to retrieve it you can initialize a class A object to deserialize it. Here is the code example
class A
attr_reader :attr1, :attr2, :attr3
def initialize(attr1:, attr2:, attr3:)
#attr1 = attr1
#attr2 = attr2
#attr3 = attr3
end
def attributes
{
attr1: attr1,
attr2: attr2,
attr3: attr3
}
end
end
class User < ApplicationRecord
# class_object => json type column in users table
def class_object
A.new(**self[:class_object])
end
end
a = A.new(attr1: 1, attr2: 2, attr3: 3)
user = User.create(class_object: a.attributes)
user.class_object # => will return object from class A