Read the docs on properties and you'll see a statement about using:
value: function() { return []; }
In relation to arrays and objects with the appropriate change to the
function.
On Mar 18, 2016 07:42, "Rob Stone" <[email protected]> wrote:
> I've just discovered something that is a little confusing and was hoping a
> polymer expert could explain what is going on :)
>
> I've defined an element with an array property (initialised to empty) with
> an attach method that then uses 'this.push' to add items to the array. If I
> then create multiple instances of the element, in the browser debugger it
> looks like the array is shared across all of these instances as each
> subsequent copy of the element seems to inherit the array values from
> previous elements. What's even more confusing is that if I create a
> dom-repeat that iterates over the array, it shows the 'correct' values for
> each instance, ie. it seems to be using an array that doesn't have
> duplicate values in it.
>
> I have a very small test project that shows this problem, however I
> haven't got anywhere to host it so cannot put a link up.
>
> Cut down code follows:
>
> <dom-module id="test-element">
> <template>
> <template is="dom-repeat" items="[[items]]">
> <content></content>
> <div>[[item]]</div>
> </template>
> </template>
>
>
> <script>
> (function () {
> Polymer({
> is: 'test-element',
> properties: {
> items: {
> type: Array,
> value: []
> }
> },
>
>
> attached: function () {
> console.log('attached');
> this.push('items', "1");
> this.push('items', "2");
> this.push('items', "3");
> console.log('items=' + this.items); // The 1st instance
> of the element displays 'items=1,2,3' the 2nd displays 'items=1,2,3,1,2,3'
> !!!!
> }
> });
> })();
> </script>
> </dom-module>
>
> <!DOCTYPE html>
> <head>
> <title>instance test</title>
> <script
> src="bower_components/webcomponentsjs/webcomponents-list.min.js"></script>
> <link rel="import" href="test-element.html"></link>
> </head>
> <body>
> <test-element>One</test-element>
> <test-element>Two</test-element>
> </body>
> </html>
>
>
>
> I'm hoping this is a simple misunderstanding on my part, but it does have
> some slightly annoying implications for a project I am working on.
>
> Rob
>
> Follow Polymer on Google+: plus.google.com/107187849809354688692
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