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我只是偶然发现了什么,我认为奇怪的行为可能也仅仅是我的Javascript继承是如何工作的误解......继承 - 实例变量
我使用的OpenLayers,它是基于prototypejs创建类和子类。我期望在超类中声明的字段将成为类或子类的每个实例中的单独对象。这似乎并不是这种情况,正如你可以在下面的例子中看到的那样。
超类MySuperClass
定义字段collection
但即使我构建此类的多个实例,并通过子场collection
似乎是共享的,就好像它是static
?
为什么会这样,以及如何在超类的定义中安全地创建实例变量?
<script type="text/javascript" src="http://openlayers.org/dev/OpenLayers.js"></script>
<script type="text/javascript">
OpenLayers.MySuperClass = OpenLayers.Class(
{
collection: [],
initialize: function(options)
{
OpenLayers.Util.extend(this, options);
},
addItem: function(listener)
{
this.collection.push(listener);
}
});
OpenLayers.MySubClassOne = OpenLayers.Class(OpenLayers.MySuperClass,
{
initialize: function(options)
{
OpenLayers.MySuperClass.prototype.initialize.apply(this, arguments);
}
});
OpenLayers.MySubClassTwo = OpenLayers.Class(OpenLayers.MySuperClass,
{
initialize: function(options)
{
OpenLayers.MySuperClass.prototype.initialize.apply(this, arguments);
}
});
var instanceOne = new OpenLayers.MySubClassOne();
instanceOne.addItem("one");
var instanceTwo = new OpenLayers.MySubClassTwo();
instanceTwo.addItem("two");
var instanceSuperOne = new OpenLayers.MySuperClass();
instanceSuperOne.addItem("three");
var instanceSuperTwo = new OpenLayers.MySuperClass();
instanceSuperTwo.addItem("four");
alert(instanceOne.collection);
alert(instanceTwo.collection);
alert(instanceSuperOne.collection);
alert(instanceSuperTwo.collection);
</script>
是的,在构造函数中初始化集合确实修复了它。非常直观。 – pstanton