Ruby on Rails Tutorials — ActiveRecord

You can pass more than simple strings to find conditions. Arrays, ranges, and nil values can be passed as well. In this episode you will see the tricks involved with passing these odd objects to find conditions.

Did you know ActiveRecord provides class methods for performing calculations on models? You can even use these methods through associations.

No need to pass foreign keys in find conditions, just do the find through a has_many association.

Shorten simple finds considerably and improve readability by using the dynamic find_all_by and find_by methods.