Prevent attribute from being changed with "attr_readonly"

rubyonrails-talk
1

Is there a way to prevent an attribute from being changed from outside the class instance? So that after a record is created, the attribute can be read but cannot be changed from outside the class instance.

At first glance, "attr_readonly" seems to be the solution. However, will "attr_readonly" also prevent the attribute from being changed even from inside the class?

In other words, will the following method successfully change the values of attribute_a and attribute_b in model A?

1.Class A < ActiveRecord::Base 2. attr_readonly :attribute_a, :attribute_b 3. def change_attributes(new_a, new_b) 4. self.attribute_a = new_a 5. self.attribute_b = new_b 6. save! 7. end 8. end

I know I can redefine the write accessor if I want to customize the way a single attribute is changed. However here I would like to change two attributes in one transaction and prevent each attribute from being changed individually.

Thanks

2

I tried to make private the write accessor for an attribute (e.g., foo) that I want to protect by defining:

Code : - fold - unfold

   1. def foo=val    2. super    3. end

However, when I make the write accessor private, I cannot even call it from inside the class because a statement such as self.foo = val returns NoMethodError: Attempt to call private method Please help. Thanks.