Subtracting Arrays

So I didn’t know this but you can subtract arrays in Ruby. Subtracting arrays results in a new array that excludes whatever values that were in the array you subtracted. For example

[1,2,3,4,5] - [1,3,4]  #=> [2,5]

In Rails you can also do this with ActiveRecordCollections, or whatever the array form of an ActiveRecord is, and do something like

(Organization.order(:name) - @bout.organizations)