Updated attributes

rubyonrails-talk
1

Hi, Is it possible to know in a callback to know which attributes were updated? I want to do stuff only if one attribute has been updated.

Greg

2

Hi, Is it possible to know in a callback to know which attributes were updated? I want to do stuff only if one attribute has been updated.

The changed and changes methods lists changed attributes. There are also invididual predicate methods, eg name_changed?

Fred

3

Frederick Cheung wrote in post #971451:

4

Frederick Cheung wrote in post #971451:

Hi,

Is it possible to know in a callback to know which attributes were

updated?

I want to do stuff only if one attribute has been updated.

The changed and changes methods lists changed attributes. There are

also invididual predicate methods, eg name_changed?

Fred

Thanks I didn’t know that one!

Yeah me too, that’s very cool, I actually have the perfect place to apply it today

5

Yes, this is a very handy feature of ActiveRecord in Rails! Let me summarize here some related methods that come up to my mind: - changed? predicate if any attributes have been updated - name_changed? described above - name_was restores the previous value - name_change [old_value, new_value] - changed [list_of_changed_attributes] - changes [hash_of_changed_attributes_with_values]