Uniq by object attribute in Ruby

Question

What\'s the most elegant way to select out objects in an array that are unique with respect to one or more attributes?

These objects are stored in ActiveRecord so us

Answer 1

I like jmah's use of a Hash to enforce uniqueness. Here's a couple more ways to skin that cat:

objs.inject({}) {|h,e| h[e.attr]=e; h}.values

That's a nice 1-liner, but I suspect this might be a little faster:

h = {}
objs.each {|e| h[e.attr]=e}
h.values

Answer 2

You can use this trick to select unique by several attributes elements from array:

@photos = @photos.uniq { |p| [p.album_id, p.author_id] }