Learning Rails

Finding Data with ActiveRecord

The find method is common in Rails, usually in controllers. It’s constantly used as find(id) to retrieve a single record with a given id, and also used as find(:all) to retrieve an entire set of records. The find method is, however, capable of much more finesse, letting you control which records are returned and in what order. There are four basic ways to call find, and then a set of options that can apply to all of those uses:

find by id

The find method is frequently called with a single id, as in find(id), but it can also be called with an array of ids, like find (id1, id2, id3, ...) in which case find will return an array of values. Finally, you can call find ([id1, id2]) and retrieve everything with id values between id1 and id2.

find all

Calling find with an argument of :all will return all the matching values as an array. (You can also abbreviate find(:all) to just .all—User.all, for example.)

find first

Calling find with an argument of :first will return the first matching value only. You’ll probably want to specify :order to be certain which value you get. (You can also abbreviate find(:first) to just .first—User.first, for example.)

find last

Calling find with an argument of :last will return the last matching value only. As with find(:first), you’ll probably want to specify :order to be certain which value you get. (Again, you can abbreviate find(:last) to just .last—User.last, for example.)

The options give you much more control over what is queried ...