Question

In a Rails application, I have a particular form with many fields for editing a resource. Since I also want to log what was changed for this particular resource, I need to know which params changed.

Currently in this form, I have duplicated every field in the form with hidden field tags, so in the controller every field is compared to the corresponding hidden field to determine if the value was changed. But it’s a LOT of work in the view and in the controller.

Being relatively new to Rails, I’m finding all kinds of Rails “magic” as I go along, so I wonder: does the framework provide a way to do this for me? Or is this pretty much the only way?

Answer 1

ActiveModel has exactly what you’re looking for, take a look at the examples in the docs…

http://api.rubyonrails.org/classes/ActiveModel/Dirty.html

person = Person.find_by_name('Uncle Bob')
person.changed?       # => false
person.name = 'Bob'
person.changed?       # => true
person.name_changed?  # => true
person.name_was       # => 'Uncle Bob'
person.name_change    # => ['Uncle Bob', 'Bob']
person.name = 'Bill'
person.name_change    # => ['Uncle Bob', 'Bill']