Backbone.js处理属性是数组 [英] Backbone.js Handling of Attributes That Are Arrays
问题描述
我真的很喜欢Backbone，但我最难做的事情似乎很简单。感谢以下示例的任何帮助。
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.
我有一个模型，Criteria，我想用它来存储我的UI中某些项目的状态。有一些简单的属性，一个属性是一个ID数组，用于存储用户在UI中选择的标记的ID。
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.
所以，我创建一个新的实例。我在tags数组中添加了一些项目。然后，我想重新开始，创建一个新实例，分配给同一个变量。但是，我的标签数组继续保存我作为第一个Criteria实例的一部分添加的信息。
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.
我已经记录了下面的测试用例。
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>
我在这里是不是很划算？我是否尝试使用Backbone来实现它的目的？或者我在javascript OO编程中遗漏了一些更普遍的东西？
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。我最初使用了Backbone标签集合，但是它提出了一系列不同的问题，这些问题与多个集合中引用的Tag模型有关，以及当从任何集合中删除项目时，Backbone的remove方法如何取消设置集合引用。另一天，另一个问题。
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.
推荐答案
Thom Blake说明为什么它保持数组的相同值。解决此问题的一个选项是在初始化程序中设置默认值
Thom Blake is right about why it's keeping the same values for the array. one option for solving this is to set the default value in the initializer
var Criteria = Backbone.Model.extend({
defaults: {
"status": "Normal",
"priority": "Normal"
},
initialize: function(){
if( !this.get('tags') ){
this.set({tags: new Array()});
}
}
});
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