Bind parameters of two polymer components inside repeat template - html

Question

I would like to bind attr and attr1 in the following example. These two parameters do not depend on data (other attributes do). When using the binding this way, there is only one shared data object between all 'rows'. I want only the two components of one iteration to be bound together.
<template repeat"{{data in dataList}}">
<component1 attr="{{binding}}" />
<component2 attr2="{{binding}}" />
</template>
My first idea was to bind the attributes to an variable of the data object:
<template repeat"{{data in dataList}}">
<component1 attr="{{data.binding}}" />
<component2 attr2="{{data.binding}}" />
</template>
This solution on the other hand is really ugly, because the model object get's view-only data attached. Because the model lives normally longer than the components, this could cause a huge overhead. Another problem is serialization, which could fail because of the attached data.
Is there any elegant solution? The only one I imagined so far is to wrap the data objects before iterating over the data set. This approach on the other hand would probably make problems with model updates...
Naive thought: Shouldn't be the scope of a variable that is only used inside of a template restricted to this template? In the special case of the repeat template furthermore to one iteration?

Answer 1

You might type-suggest your binding variable being an Object and use it like:
<polymer-element name="my-element" attributes="dataList">
<template>
<ul>
<template repeat="{{d in dataList}}">
<li>
{{d}} ⇒ {{binding[d]}} <!-- Since type-suggested, it works -->
</li>
</template>
</ul>
</template>
<script>
Polymer({
dataList: ['navy', 'maroon'],
binding: {} /* it’s necessary to type-suggest var for Polymer */
});
</script>
</polymer-element>
Please be aware that the snippet above expects different items in dataList. Live preview: http://plnkr.co/edit/ez36BVUPCKW8xRSkGxOM?p=preview
Naive thought: Shouldn't be the scope of a variable that is only used inside of a template restricted to this template? In the special case of the repeat template furthermore to one iteration?
This sounds impossible for me, because (besides that this will overcomplicate the implementation) sometimes one wants to bind the variable in nested template:
<template repeat="{{a in lst}}">
{{bound_here}}
<template id="nested">
{{bound_here}}
...
With what you suggested the binding above becomes impossible.