Rails Active Record - Get ids array from relation

Have been reading through the rails 4 docs and it looks like they support the ids method that I said would be cool in the question now.

http://api.rubyonrails.org/classes/ActiveRecord/Calculations.html#method-i-ids

Nice to know the team are reading my mind :)

A little bit more neat solution:

Product.where(:colour => 'blue').pluck(:id)

In recent versions of Rails the ids method can be used.

Product.where(color: 'blue').ids