我可以将Flex组件属性绑定到函数吗？

Question

我想根据具有一个或多个参数的函数的返回值在按钮上设置enabled属性.我怎样才能做到这一点？

private function isUserAllowed (userName:Boolean):Boolean {
   if (userName == 'Tom')
      return true;
   if (userName == 'Bill')
      return false;
}

<mx:Button label="Create PO" id="createPOButton"
enabled="<I want to call isUserAllowed ('Bill') or isUserAllowed ('Tom') here>"
click="createPOButton_Click()" />

Answer 1

根据Flex文档,只要该属性是可绑定的,您可以简单地执行此操作(我已经包含了两个额外的按钮来演示):

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">

    <mx:Script>
        <![CDATA[

            [Bindable]
            private var currentUser:String = "Bill";

            private function isUserAllowed(user:String):Boolean
            {
                if (user == "Bill")
                {
                    return true;
                }

                return false;
            }

        ]]>
    </mx:Script>

    <mx:VBox>
        <mx:Button label="My Button" enabled="{isUserAllowed(currentUser)}" />
        <mx:HBox>
            <mx:Button label="Try Tom" click="{currentUser = 'Tom'}" />
            <mx:Button label="Try Bill" click="{currentUser = 'Bill'}" />
        </mx:HBox>
    </mx:VBox>

</mx:Application>

如果没有currentUser标记为[Bindable],它将无效.

另一种方法,如果你想更多地按字母顺序绑定到函数(这也在文档中表示),那就是让函数响应当前用户更改时发送的事件,如下所示:

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" initialize="init()">

    <mx:Script>
        <![CDATA[

            private var _currentUser:String = "Bill";

            public function set currentUser(value:String):void
            {
                if (_currentUser != value)
                {
                    _currentUser = value;
                    dispatchEvent(new Event("userChanged"));
                }
            }           

            [Bindable(event="userChanged")]
            private function isUserEnabled():Boolean
            {
                if (_currentUser == "Bill")
                {
                    return true;
                }

                return false;
            }

        ]]>
    </mx:Script>

    <mx:VBox>
        <mx:Button label="My Button" enabled="{isUserEnabled()}" />
        <mx:HBox>
            <mx:Button label="Try Tom" click="{currentUser = 'Tom'}" />
            <mx:Button label="Try Bill" click="{currentUser = 'Bill'}" />
        </mx:HBox>
    </mx:VBox>

</mx:Application>

所以有两种方法.IMO,第二个似乎更合适,但第一个肯定没有错.祝好运!

Answer 2

<mx:Button
enabled = "{this.myFunction(this.myVariable)}"
>

或内联:

<mx:Button
enabled = "{(function(arg:Object):Boolean{ ... })(this.myVariable)}"
>