Question

Goal

I have a top-level Collection named Players and a Session variable called ‘n’. In addition to my top-level Collection, I’d like to have a Collection of the top-‘n’ Players based on player.points, which updates in reaction to Session.set('n', n) (and, of course, any changing of the underlying Players data).

Rationale

The reason I would like a TopNPlayers is because within each player template (call it Template.player_item) I want to provide a couple of variables:

• Template.player_item.isInTopN, which sets a CSS class to highlight a player if it’s in the top-‘n’ in points
• Template.player_item.PointsVsBaseline, which gives the difference between that player’s points and the ‘n’th player in TopNPlayers.

Since I don’t want to manually manage a global variable containing Players filtered by the value of Session.get('n'), and I certainly don’t want to calculate the top-‘n’ every time I render another player_item, I’d like to set up an additional subscription to the Players Collection.

Answer 1

I’m not sure you need a separate collection, wouldn’t a cursor do the trick?

Something like:

var topNPlayers = function() { 
  return Players.find({}, {limit: Session.get('n')}); 
}

Template.player_item.isInTopN = function() {

  // there are a bunch of ways you could do this step...
  _.include(topNPlayers().fetch(), this);
}