jQuery的droppable的hoverClass的回调函数参数的问题

导入
[code="java"]

[/code]
然后有如下代码
[code="java"]
$('elementId').droppable({
accept: ".file, .folder",
hoverClass: function(e, ui) {
alert(typeof(ui));
alert(ui.helper);
}
}
[/code]
这里alert(typeof(ui))出的type居然是string。alert(ui.helper)居然是undefined。
按照jQuery UI的文档[code="java"]All callbacks receive two arguments: The original browser event and a prepared ui object, view below for a documentation of this object (if you name your second argument 'ui'):

* ui.draggable - current draggable element, a jQuery object.
* ui.helper - current draggable helper, a jQuery object
* ui.position - current position of the draggable helper { top: , left: }
* ui.offset - current absolute position of the draggable helper { top: , left: }

[/code]
不应该这样吧。或者还是我用的不对？
怎样才能向hoverClass的回调函数传递自己需要的参数呢？

[quote]
[code="javascript"]
$('#block').arrt("cond", tree);// 这样添加？好像不行啊
[/code]
[/quote]
你写错了，是“attr”。另外，直接绑定对象到DOM节点上设置属性只能字符串值。你可以把你的TreeClass分解成多个字符串值属性，绑定到节点上。

[quote]
hoverClass

Type:
String
Default:
false

If specified, the class will be added to the droppable while an acceptable draggable is being hovered.
[/quote]
文档里只说hoverClass是个String，没说过它是个回调函数啊！

[code="html"]
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">

Untitled

<br> $(function(){<br> $(".file").draggable();</p> <pre><code> $('#block').droppable({ accept: ".file, .folder", hoverClass: "hover" }); }); </script> <style type="text/css"> .hover{ background:#99abc3; } </style> </code></pre> <p></head></p> <p><body><br> <div id="block" style="border:1px solid #ab4;height:300px;"><br> Hello World!<br> </div><br> <div class="file" style="border:1px solid red;width:300px;"><br> <p>Drag me to my target</p><br> </div><br> </body><br> </html><br> [/code]<br> 是这样的，我写的例子。</p>

[quote]
All callbacks receive two arguments: The original browser event and a prepared ui object, view below for a documentation of this object (if you name your second argument 'ui'):

* ui.draggable - current draggable element, a jQuery object.
* ui.helper - current draggable helper, a jQuery object
* ui.position - current position of the draggable helper { top: , left: }
* ui.offset - current absolute position of the draggable helper { top: , left: }

[/quote]
它说的回调方法指的是Event的回调。
对于hoverClass，这个只是options里的一个设置选项，默认是false，并不是一个回调函数：
[code="javascript"]
_over: function(event) {

    var draggable = $.ui.ddmanager.current;
    if (!draggable || (draggable.currentItem || draggable.element)[0] == this.element[0]) return; // Bail if draggable and droppable are same element

    if (this.accept.call(this.element[0],(draggable.currentItem || draggable.element))) {
        if(this.options.hoverClass) this.element.addClass(this.options.hoverClass);
        this._trigger('over', event, this.ui(draggable));
    }

}

[/code]
这是droppable里的源代码，看实现知道，它是通过addClss来实现的，而addClass接受的参数可以是string或function：
[code="javascript"]
addClass: function( value ) {
if ( jQuery.isFunction(value) ) {
return this.each(function(i) {
var self = jQuery(this);
self.addClass( value.call(this, i, self.attr("class")) );
});
}

    if ( value && typeof value === "string" ) {
        var classNames = (value || "").split( rspace );

        for ( var i = 0, l = this.length; i < l; i++ ) {
            var elem = this[i];

            if ( elem.nodeType === 1 ) {
                if ( !elem.className ) {
                    elem.className = value;

                } else {
                    var className = " " + elem.className + " ", setClass = elem.className;
                    for ( var c = 0, cl = classNames.length; c < cl; c++ ) {
                        if ( className.indexOf( " " + classNames[c] + " " ) < 0 ) {
                            setClass += " " + classNames[c];
                        }
                    }
                    elem.className = jQuery.trim( setClass );
                }
            }
        }
    }

    return this;
}

[/code]
所以下面的写法效果和我之前的一样：
[code="javascript"]
$('#block').droppable({
accept: ".file, .folder",
hoverClass: function() {
return "hover";
}
});
[/code]

如果你要通过条件来显示hover的class，可以条件以属性的形式设到要droppable的对象上，然后在用hoverClass时，设为函数，这样获取外部条件值：
[code="javascript"]
$('#block').droppable({
accept: ".file, .folder",
hoverClass: function() {

    return "hover";
}

});

[/code]

抱歉，前面没写完，重写：
[code="javascript"]
$('#block').droppable({
accept: ".file, .folder",
hoverClass: function(){
var condition = $(this).attr("cond");
return condition ? "hover" : "another-hover";
}
});
[/code]
这里“cond”就是设定到对象上的条件值。