What do you mean by "update the whole project" ? Generate Scaffold again for it?
rails g scaffold <model>
You will have to overwrite the already generated files.
If you have made important changes to the generated files I strongly advise you to do the manual editing (add the field to the views, controllers, etc.).
Don’t forget that if you didn’t use Migration to create this change, just changing the main migration file does not reflect in db:migrate. In this case, you would have to drop the database (db:drop), create it again (db:create), and then migrate (db:migrate). Just BEWARE of these steps because it will erase everything you already have of record, so for migrations always use the command:
rails g migration <acao>
Related links:
- Migrations