How to make database field readonly in rails.

Question

Hey folks,

I have a database table with a certain field which should be impossible to update once it has been inserted to the database. How do I tell my model that it shouldn't allow updating of a certain field?

Best Regards, x3ro

Answer 1

My rails is rusty, but I think that something like the following would do the trick:

def foo= (val)
    raise DontDoThatException.new
end

Answer 2

You want to use attr_readonly.

From the docs: "Attributes listed as readonly can be set for a new record, but will be ignored in database updates afterwards"

class Customer < ActiveRecord::Base
    attr_readonly :your_field_name
end

Answer 3

And that field is always and by definition "correct" (i.e. an accurate representation of reality) at the time of insertion ?

No user ever makes a mistake when entering that field for the first (and in your scheme : only) time ?