Question: If I have a class that looks like below, how to I pull out just the last name from each instance a collection into an array?

```
class Person
  include :Mongoid::Document

  field :first_name
  field :middle_name
  field :last_name
  field :email_address

end

Person.all # What do I do after I have the collection?

```

Answer: 
`Person.all.map(&:last_name)` will do it
Person.where(...search...).only(:last\_name)

<http://mongoid.org/docs/querying/criteria.html#only>