我可以绑定一个Flex组件属性的功能？

Question

我想设置的 启用 在基于具有一个或多个参数的函数的返回值的按钮属性。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

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

或内联：

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

Answer 2

据到Flex文档，只要属性是可绑定的，你可以简单地做到这一点（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>

无currentUser标记为[绑定]，虽然，它不会工作。

另一种方式去，如果你想更多的从字面上结合功能（这也是在docs表示），将有给你分派事件的响应函数在当前用户的变化，就像这样：

<?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>

因此，有几个方法。 IMO，第二个看起来有点更合适的，但绝对没有什么不妥之首。祝你好运！

Answer 3

下面就是我在类似情况下做了几次：

<mx:Script>
<![CDATA[

    [Bindable] var _username : String;

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

]]>
</mx:Script>

<mx:Button label="Create PO"
    id="createPOButton"
    enabled="{isUserAllowed(_username)}"
    click="createPOButton_Click()" />

此方式，当可绑定_username变化，这将会触发改变通知。由于标签是听_username变化（即使它是简单地另一功能的参数），则enabled属性将被重新评估。

Answer 4

<mx:Script>
    <![CDATA[
        [Bindable]
        private var userName : String = "Tom"; // or whatever ...
        [Bindable]
        private var userAllowed : Boolean;

        private function isUserAllowed ():Boolean {
           if (userName == 'Tom')
             return false;
           if (userName == 'Bill')
              return false;
           return false;
        }
    ]]>
</mx:Script>

    <mx:Button label="Create PO" id="createPOButton" enabled="{userAllowed}" addedToStage="isUserAllowed()"/>