Rails%203%20In%20Action

Attribute change tracking
Of course this method will return true, because you changed your name attribute previously.
In addition to this, you’re even able to see what the value was before the
change using the *_was method:
>> project.name_was
=> nil
This time, name was nil before you set it and so nil is returned. If it had a value
before you created this object, it would return that instead. Finally, you can even get
back an array containing the before and after values of the attribute by using the
*_change method:
>> project.name_change
=> [nil, "Ticketee"]
Now, what would these methods be used for? Well, any number of things, really. You
could use it for only running a certain callback if a specific field had been changed, or
you could use the *_change methods to log the changes to attributes in another table
if you wish.
549