Structuring session variables to minimize template rerendering - meteor

Question

I am currently developing my first Meteor project, and as the code basis is growing, I am unsure about using session variables/ the reactive programming approach correctly. For example, let's have a look at a form for editing a blog article. Before editing, I use Session.set("current_article", Articles.findOne(id)) to set the current article. When opening the article form, everything is populated correctly by using <input type="text" name="title" value="{{article.title}}">.
But the form is much more complicated than just displaying the title:
E.g. when the title or a tag changes, the text on right the right (a generated tweet message) updates while typing. To achieve this, I register a keyUp listener that sets Session.set("current_article", $.extend(Session.get("current_article"), {tweet: someMagicTweetGeneration()})). You might already notice that the way I am using Session variables causes rerendering the whole template.
So my question is: Does it makes sense storing more complex objects (like articles) into a session variable? This way saving the form is quite straightforward, but it obviously causes other issues. Should I split Session.get("current_article") into Session.get("current_article.title"), Session.get("current_article.tweet"), ...? Any other best practices?

Answer 1

You could use {{#isolate}}..{{/isolate}} blocks so that only bits of your template are re-rendered and not the entire thing, e.g with:
{{#isolate}}
<input type="text" name="title" value="{{article.title}}">
{{/isolate}}
So now when you change article.title only the bits inside this isolate block will be changed, and everything surrounding will be untouched.
You do have to re-render bits of the DOM that change, so the idea is to only re-render the bits that need to be redrawn.
As for the Session variables, try storing them in a manner where if you send out the variable to the DOM, to avoid sending one large object and instead send only the pieces that are required for a template.
E.g in the above you might have many things used in {{article}}, but you only use {{article.title}} in that bit of code, so it might be better to use only template. If you know you're going to use all of them then you might as well use nested objects.

Answer 2

I want to bet on meteor getting better and better, so we don't have to jump through those kinds of hoops. I imagine you already know about http://docs.meteor.com/#template_preserve.
I would suggest you try splitting the data into two distinct structures in the session, main and sidebar. Have each template react to only one or the other. That may even be a reasonable schema for your mongo collections.
I read something about optimizing that suggested you store ids in the session, rather than whole objects, then just findOne for the collection.
Is this a hypothetical problem, or are there symptoms you are bothered with?