Question

I have a Ruby array which contains Post objects (a Mongoid model) with a created_at method returning a Time object. What I want is to sort that array using that method (which is present on every element on the array). I tried @posts.sort_by {|post| post.created_at} but that didn’t work. How could I achieve this? Thanks!

EDIT: Example of the array:

[#<Post _id: 4ffd5184e47512e60b000003, _type: nil, created_at: 2012-07-11 10:12:20 UTC, title: "TestSecond", description: "TestSecond", slug: "assa", user_id: 4ffc4fd8e47512aa14000003>, #<Post _id: 4ffd518ee47512e60b000004, _type: nil, created_at: 2012-07-11 10:12:30 UTC, title: "TestFirst", description: "TestFirst", slug: "assadd", user_id: 4ffc4fd8e47512aa14000003>].

EDIT #2: I’m getting that @posts arra with:

@posts = Array.new

@user.following.each do |user|
   user.posts.each do |p|
    @posts << p
   end
end

Answer 1

I’m not sure why you have an array here. Normally, with Mongoid querying, you should have a Mongoid::Criteria instance, which you can desc(:created_by) or asc(:created_by) on, in order to sort.

Still, can’t think of any reason sort_by doesn’t work for properly for you, works great on my app (just tried at console).

UPD:

@user.following.each do |user|
   user.posts.each do |p|
    @posts << p
   end
end

Well, to still have a mongoid collection there, something like this might be done:

@posts = @user.following.map(&:posts).inject { |posts, post| posts.concat post }

Now, you can @posts.desc(:created_at).

UPD2:

Also, for purpose of having a cleaner code, you could define a posts_from_following on User:

class User
  def posts_from_following
    following.map(&:posts).inject { |posts, post| posts.concat post }
  end
end

and then, just do

@posts = @user.posts_from_following.desc(:created_at)

in your controller.