Vaadin-Grid Polymer Element migration from cell renderer - polymer

Question

In Polymer 1.0 and Vaadin-grid v1 I was using a cell renderer along the following lines to add an icon based on the value of the data:
grid.columns[6].renderer = function(cell) {
if (cell.data < 0){
cell.element.innerHTML = Math.abs(cell.data) + '<iron-icon icon="arrow-downward" style="color: red"/>';
}
else if (cell.data > 0) {
cell.element.innerHTML = cell.data + '<iron-icon icon="arrow-upward" style="color: green"/>';
}
else {cell.element.innerHTML = '<iron-icon icon="settings-ethernet" style="color: #ffcc00"/>';}
};
Of course the migration to vaadin-grid 2 means no more renderer function and recommendation to use templates instead.What would be the most efficient way to achieve this?
Any help appreciated - I'm kind of learning this stuff as I go along and the examples on the vaadin site assume a bit more expertise than I have !

Answer 1

Tomi Virkki over on the Vaadin forum was kind enough to post me a simple example using computed bindings.Seems obvious now it has been explained .. gotta learn somehow I guess! Thanks Tomi
<vaadin-grid items="[[users.result]]">
<vaadin-grid-column width="50px" flex-grow="0">
<template class="header">#</template>
<template>
<iron-icon icon="[[_itemIcon(item)]]" style$="[[_itemIconStyles(item)]]"/>
</template>
</vaadin-grid-column>
<vaadin-grid-column>
<template class="header">First Name</template>
<template>[[item.firstName]]</template>
</vaadin-grid-column>
<vaadin-grid-column>
<template class="header">Last Name</template>
<template>[[item.lastName]]</template>
</vaadin-grid-column>
</vaadin-grid>
</template>
<script>
window.addEventListener('WebComponentsReady', () => {
class XGrid extends Polymer.Element {
static get is() {
return 'x-grid';
}
_itemIcon(item) {
return item.firstName > 'N' ? 'arrow-upward' : 'arrow-downward';
}
_itemIconStyles(item) {
return `color: ${item.firstName > 'N' ? 'green' : 'red'}`;
}
}
customElements.define('x-grid', XGrid);