More readable for ActiveRecord statements using Placeholder Conditions
Here’s another readability hack for Ruby ActiveRecord code. It’s called “Placeholder Conditions.”This:
where("start_time < :time", time: Time.now)
works the same as this
where("start_time < ?", Time.now)
The second is more terse, but if you are inserting a lot of values into the WHERE statement, then the first is nice for readability.
Source: Ruby on Rails Guides