ActiveHash instance should not be editable

[syguer]

Relating #125
ActiveHash focus on master data. So I think we should drop( or prohibit) editing(update/destroy) on version 2.0.0.
(but, it is easy to change instance value on Ruby. I mean we should drop it from open API)

I know it is very aggressive change so I want to hear your opinion.

[stcorbett]

hmm... Instance variables are core functionality for ruby objects. They are less known or used in rails-land, I'd suspect a rails app that modifies them during a request probably confuses more rails users than it helps...

Having a strict and clear "don't use instance variables on these objects" policy sounds better than an unclear policy and unexpected behavior which is more of what is in place at the moment.

Is there an straightforward way to "turn them off" for ActiveHash objects?
Do you know of other ruby/rails objects that restrict instance variable functionality?

[syguer]

I think it is OK to use instance variables, problem is not to be valid access permission.
Encapsulation is base theory of Object-Orientated programming. Ruby object can access to instance variables doesn't through accessor(like #set_instance_valiables). Able to do is not always OK to do, isn't it?

Having a strict and clear "don't use instance variables on these objects" policy sounds better than an unclear policy and unexpected behavior which is more of what is in place at the moment.

Sounds good. we should do.

I closed your PR once. But I'm going to reopen & merge if we have no idea for strict value of ActiveHash 🤔

[syguer]

Oh sorry, our discussion point was not matching, and I finally understand.
A things you want is finder should not return original instance. Right?
It seems to be unrelated to instance variables. I'm OK to fix it.

Let's taking about this issue on #124