Fuzzifized Fuzzifized - 19 days ago 16
Javascript Question

Pushing to data-bound array used in dom-repeat (Polymer)

I have a data-bound array (

dom-repeat
) in a custom Polymer element, and I need to push new data into the array. It's not displaying the items, even though it knows 2 elements have been added. What am I missing here?

jsFiddle

<link rel="import" href="../../bower_components/polymer/polymer.html">

<dom-module id="main-element">
<template>
<ul>
<template is="dom-repeat" items="{{people}}">
<li>{{item.first}}</li>
</template>
</ul>
</template>

<script>
(function() {
'use strict';
Polymer({
is: 'main-element',
properties: {
people: {
type: Array,
value: function() {
return [];
}
}
},
ready: function() {
// Mock data retrieval
this.people.push({"first": "Jane", "last": "Doe"});
this.people.push({"first": "Bob", "last": "Smith"});
}
});
})();
</script>



Answer

Use Polymer's array mutation methods when pushing items into the array:

this.push('people', {"first": "Jane", "last": "Doe"});
this.push('people', {"first": "Bob", "last": "Smith"});

<head>
  <base href="https://polygit.org/polymer+1.7.0/components/">
  <script src="webcomponentsjs/webcomponents-lite.min.js"></script>
  <link rel="import" href="polymer/polymer.html">
</head>

<body>
  <main-element></main-element>

  <dom-module id="main-element">
    <template>
      <ul>
        <template is="dom-repeat" items="{{people}}">
          <li>{{item.first}}</li>
        </template>
      </ul>
    </template>

    <script>
      HTMLImports.whenReady(function() {
        'use strict';
        Polymer({
          is: 'main-element',
          properties: {
            people: {
              type: Array,
              value: function() {
               return [];
              }
            }
          },
          ready: function() {
            // Mock data retrieval
            this.push('people', {"first": "Jane", "last": "Doe"});
            this.push('people', {"first": "Bob", "last": "Smith"});
          }
        });
      });
    </script>
  </dom-module>
</body>

codepen

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