sorting a ruby array of objects by an attribute that could be nil

Question

I have an array of objects that I need to sort by a position attribute that could be an integer or nil, and I need the objects that have the nil position to be at the end of

Answer 1

You can do this without overriding the spaceship operator by defining a new comparison method.

class Child
  include Comparable   
  def compare_by_category(other)
    return 0 if !category && !other.category
    return 1 if !category
    return -1 if !other.category
    category.position <=> other.category.position
  end
end

The sort method can take a block, so you can then sort using this new method:

children.sort {|a,b| a.compare_by_category(b) }