Ruby sort based on predefined list

Question

I have an array of objects. Each object has an attribute we'll call display_name.

I want to sort this array based on a predefined list of values.

So if the predefined list looks something like this ["Ball", "Cat", "Helicopter", "France"]

Then the objects with the display_name attribute matching "Ball" with be at the head of the list, those with "Cat" second in the list and so on and so forth.

Answer 1

You can use Enumerable#sort_by:

list = ["Ball", "Cat", "Helicopter", "France"] 
elements = [{:display_name => 'Cat'}, {:display_name => 'Unknown'}, {:display_name => 'Ball'}]

# sort by index in the list. If not found - put as last.
elements.sort_by { |e| list.index(e[:display_name]) || list.length } 
# => [{:display_name=>"Ball"}, {:display_name=>"Cat"}, {:display_name=>"Unknown"}]