Blaze.renderWithData - how to automatically update template if data changes?

Question

I have built a list using Meteor. I do not want the entire list to be reactive, i.e. auto-update when the data changes. However, I do want the title of a list item to update if the data relating to that list item changes. I am inserting the list items using Blaze.renderWithData, so how can I achieve this?

Answer 1

Use two helpers, a non-reactive one which returns the cursor and a reactive one which returns the title. To make something non-reactive, use Tracker.nonreactive, (related question).

In the following contrived example I'm returning a reactive title that includes the cursor count if non-zero while the cursor returned from the helper is non-reactive.

subHandle = Meteor.subscribe('mySubscription');

Template.foo.helpers({
  cursor: function(){
    if ( subHandle.ready() ) return Tracker.nonreactive(function() {
      return myCollection.find(query,options);
    });
  }),
  title: function(){
    var nDocs = myCollection.find(query,options).count();
    if ( nDocs ) return "Title (" + nDocs + ")";
    else return "Title";
  }
});

Update: Modified to deal with the subscription handle being ready so that the nonreactive function is called for the first time with a ready subscription.

Here's a Meteorpad with a working example. You can see that the total points updates as you add points to players but the player scores and sort never change.