I really like Backbone, but I am having the hardest time doing what would seem to be simple things. I appreciate any help with the following example.
I have a model, Criteria, that I want to use to store the state of some items in my UI. there are a couple simple attributes, and one attribute that is an array of IDs used to store the IDs of tags the user has selected in the UI.
So, I create a new instance. I add some items to the tags array. Then, I want to start fresh, create a new instance, assigned to the same variable. But, my tags array continues to hold information I added to it as a part of the first instance of Criteria.
I have documented the test case below.
<!DOCTYPE html PUBLIC -//W3C//DTD XHTML 1.0 Transitional//EN http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd>
<html xmlns=http://www.w3.org/1999/xhtml>
<head>
<title>Test</title>
<script src=Scripts/Libraries/jquery-1.6.1.js type=text/javascript></script>
<script src=Scripts/Libraries/underscore.js type=text/javascript></script>
<script src=Scripts/Libraries/backbone.js type=text/javascript></script>
<script language=javascript type=text/javascript>
$(function () {
// Simple model to hold some state about my UI.
var Criteria = Backbone.Model.extend({
defaults: {
status: Normal,
priority: Normal,
tags: new Array()
}
});
// Create new criteria.
window.criteria = new Criteria();
// The length of the tags array should be 0. PASSES
console.log(Expect 0: Actual + window.criteria.get(tags).length);
// Add a tag id to the tags array.
window.criteria.get(tags).push(5); // Tag with ID of 5.
// The length of the tags array should be 1. PASSES
console.log(Expect 1: Actual + window.criteria.get(tags).length);
// Create a new instance of criteria.
window.criteria = new Criteria();
// The length of the tags array should be 0. FAILS
// CONFUSED. I thought this is now a new instance with a new set of attributes.
// Why does the tags collection still have an item in it.
console.log(Expect 0: Actual + window.criteria.get(tags).length);
// OK. So, I will call the clear method on the model. This is supposed to remove all attributes
// from the model.
// Then, I will create it again.
window.criteria.clear();
window.criteria = new Criteria();
// The length of the tags array should be 0. FAILS. Still 1.
console.log(Expect 0: Actual + window.criteria.get(tags).length);
// ARGH!
console.log(HELP!);
});
</script>
</head>
<body>
<h1>Test</h1>
<p>Backbone test page.</p>
</body>
</html>
Am I just way off the mark here? Am I trying to use Backbone for things it was not intended? Or am I missing something more general in javascript OO programming?
P.S. I originally used a Backbone collection of tags, but that presented a whole different set of issues relating to having a Tag model referenced in multiple collections and how Backbone's remove method unsets the collection reference when an item is removed from any collection. Another day, another issue.
