[Ruby,Sinatra,Datamapper] How to select elements by association order by father ID?

Question

ruby

Hello!
I have a Mainstack model that has belongs_to :song and a Song model that has n, :mainstacks
I need to select Mainstack.all.songs but sort it by parent Mainstack ID
Mainstack.all(:order => [id] ).songs doesn't work, still sorted by songs.id

Answer 1

Since you write in ruby, then write correctly
Well, sorting can be done like this

@songs = Song.all(:order => [Song.mainstacks.id.desc])

Answer 2

@Mainstacks = Mainstack.all( :order => [:id.desc])
    @songs = []
    @Mainstacks.each do |mainstack|
      @songs << mainstack.song
    end

I did it, but it seems to me that this is not the best solution, any ideas?