Meteor: Preselected options lost after rerendering multiple select - meteor

Question

I have a multiple select with a Handlebar template in Meteor.js. On first rendering, everything is fine ("Politics" and "People" are preselected as expected):
As soon as the template has to be rerendered (because a Session variable changes, e.g. Session.set("foo", "Hello World!")), the third option is not preselected anymore:
My setup:
<template name="select">
<select name="foo" multiple>
<option value="1">Tech</option>
<option value="2" selected>Politics</option>
<option value="3" selected>People</option>
</select>
</template>
<template name="test">
{{foo}}
{{> select}}
</template>
{{> test}}
Template.test.helpers(
foo: ->
Session.get("foo")
)
Do you have any idea why the options are preselected anymore after rerendering?

Answer 1

Solution is:
<template name="test">
{{#isolate}}
{{foo}}
{{/isolate}}
{{> select}}
</template>
Typically, the exact extent of re-rendering is not crucial, but if you
want more control, such as for performance reasons, you can use the
{{#isolate}}...{{/isolate}} helper. Data dependencies established
inside an #isolate block are localized to the block and will not in
themselves cause the parent template to be re-rendered. This block
helper essentially conveys the reactivity benefits you would get by
pulling the content out into a new sub-template.
If you put {{foo}} inside {{#isolate}} ... {{/isolate}} then parent template won't be rerendered, so also {{> select}} won't be affected.

Answer 2

So I am not sure why you are loosing the multiple select but I can recommend you put an {{#isolate}} tag around your{{> select}} template. That should keep the template from re-rendered. Though it will not help if your select template re-renders because its data changes. Hope that helps...