How to run method of inherited class in mongodb? - ruby

Question

For example, I created ChildClass inherited from BaseClass below:
class BaseClass
end
First child class
class ChildClass1 < BaseClass
end
Or another
class ChildClass2 < BaseClass
end
When worked with BaseClass
It work as normal.
But when work with ChildClass 1 or 2,
I cannot do childclass1.count or childclass1.first
Errors as follow: (when working with child class after saved as show here)
[2] pry(#<TodosController>)> #todo = "Todo::TodoM#{$xvars["user_id"].to_s}".constantize.new
=> #<Todo::TodoM5ca1157c51d2f56bc4d5e379 _id: 5ca45c5651d2f5988c2ef5fa, created_at: nil, updated_at: nil, user_id: nil, title: nil, completed: nil, due: nil, detail: nil, image: nil, member: nil, status: nil, _type: "Todo::TodoM5ca1157c51d2f56bc4d5e379">
[3] pry(#<TodosController>)> #todo = "Todo::TodoM#{$xvars["user_id"].to_s}".constantize.new(
[3] pry(#<TodosController>)* title: $xvars["form_todo"]["title"],
[3] pry(#<TodosController>)* user_id: $xvars["user_id"])
=> #<Todo::TodoM5ca1157c51d2f56bc4d5e379 _id: 5ca45ca351d2f5988c2ef5fb, created_at: nil, updated_at: nil, user_id: BSON::ObjectId('5ca1157c51d2f56bc4d5e379'), title: "sdfsdf", completed: nil, due: nil, detail: nil, image: nil, member: nil, status: nil, _type: "Todo::TodoM5ca1157c51d2f56bc4d5e379">
[4] pry(#<TodosController>)> #todo.save!
MONGODB | localhost:27017 | todo2_development.insert | STARTED | {"insert"=>"todos", "ordered"=>true, "lsid"=>{"id"=><BSON::Binary:0x70237914801960 type=uuid data=0x0c897c8df79a4052...>}, "documents"=>[{"_id"=>BSON::ObjectId('5ca45ca351d2f5988c2ef5fb'), "_type"=>"Todo::TodoM5ca1157c51d2f56bc4d5e379", "title"=>"sdfs...
MONGODB | localhost:27017 | todo2_development.insert | SUCCEEDED | 0.006s
=> true
[5] pry(#<TodosController>)> #todo.first
NoMethodError: undefined method `first' for #<Todo::TodoM5ca1157c51d2f56bc4d5e379:0x00007fc31453c828>
from (pry):6:in `create'
[6] pry(#<TodosController>)> #todo
=> #<Todo::TodoM5ca1157c51d2f56bc4d5e379 _id: 5ca45ca351d2f5988c2ef5fb, created_at: 2019-04-03 07:11:48 UTC, updated_at: 2019-04-03 07:11:48 UTC, user_id: BSON::ObjectId('5ca1157c51d2f56bc4d5e379'), title: "sdfsdf", completed: nil, due: nil, detail: nil, image: nil, member: nil, status: nil, _type: "Todo::TodoM5ca1157c51d2f56bc4d5e379">
[7] pry(#<TodosController>)> #todo.save!
=> true
[8] pry(#<TodosController>)> #todo.count
NoMethodError: undefined method `count' for #<Todo::TodoM5ca1157c51d2f56bc4d5e379:0x00007fc31453c828>
from (pry):9:in `create'
[9] pry(#<TodosController>)> #todo.first
NoMethodError: undefined method `first' for #<Todo::TodoM5ca1157c51d2f56bc4d5e379:0x00007fc31453c828>
from (pry):10:in `create'
[10] pry(#<TodosController>)> #todo.first
NoMethodError: undefined method `first' for #<Todo::TodoM5ca1157c51d2f56bc4d5e379:0x00007fc31453c828>
from (pry):11:in `create'
[11] pry(#<TodosController>)> #todo.class
=> Todo::TodoM5ca1157c51d2f56bc4d5e379
What did I do wrong?
(Yes I see error from 'create' but it saved! as shown)
{
"_id": ObjectId("5ca45ca351d2f5988c2ef5fb"),
"_type": "Todo::TodoM5ca1157c51d2f56bc4d5e379",
"title": "sdfsdf",
"user_id": ObjectId("5ca1157c51d2f56bc4d5e379"),
"updated_at": new Date(1554275508224),
"created_at": new Date(1554275508224)
}

Answer 1

I found ChildClass will work like BaseClass. The reason that not work in the beginning because user_id was nil.
The others issue is the way mongodb handle its subclass as internally as another type of data in it's BaseClass! even though we put namespace when created. What I surprised was the mongodb response namespace from rails is different by created another collection(table) as easily understand (and that what I first looking for) instead of hidden as another _type (field) that make me confused at first. So I like to note here for newbie.
instead of something I expected below as another collection