In ruby/rails, how do I sort on a date value where the date can sometimes be null?

Question

I would like to sort my games by game_date, but sometimes the game_date may be null, and I will get an exception: undefined method `to_datetime' for nil:NilClass

@games = @teams.reduce([]) { |memo, team| memo + team.games }.sort_by(&:game_date)

Any good way of doing this?

Answer 1

If you just want to drop entries without date, simplest solution -

ar.select(&:date).sort_by(&:date)

adding nils at the end can be done with

ar.select(&:date).sort_by(&:date) + ar.reject(&:date)

If you happen to know the range of possible dates, you can be fine with something like

ar.sort_by{|e| e.date || Date.new(9999)}

BTW, reduce in your statement can be changed to (IMHO) more clear

@games = @teams.map(&:games).flatten

Answer 2

An easy way would be to split your array into those with nils and those without, then sort the non-nil half as desired and paste them together:

parts  = a.partition { |o| o.date.nil? }
sorted = parts.last.sort_by(&:date) + parts.first

This approach will work with any method (i.e. not just with date) and it should be quick enough.