String as a function name in as3 / Flex

Question

I have a custom component that extends the spark list.

Inside that custom list, I'm looking to declare a public function that can be called from the main application to filter the result of the list using filterFunction.

My problem is I have multiple filters and I need to pass the function name from the main application as a string ( Or by another way I will learn today! :-) ) like this :

My custom list

<s:List xmlns:fx="http://ns.adobe.com/mxml/2009" 
xmlns:s="library://ns.adobe.com/flex/spark" 
xmlns:mx="library://ns.adobe.com/flex/mx" dataProvider="{listView}">

<fx:Script>
    <![CDATA[

        public function applyFilter(functionName:String):void
        {
            listView.filterFunction = functionName as Function // <-- THIS DOESN'T WORK;
            listView.refresh();
        }

        private function myFilter(obj:Object):Boolean
        {
            // Execution code
        }

        private function anotherFilter(obj:Object):Boolean
        {
            // Execution code
        }

    ]]>
</fx:Script>

Call from my main app

<fx:Script>
<![CDATA[

private function callMyCustomListFilter():void
{
    myCustomList.applyFilter('myFilter');
}

]]>

No error, nothing. The filterFunction is just not executed... Can somebody help? Thanks a lot!

Answer 1

My problem is I have multiple filters and I need to pass the function name from the main application as a string

Pass the function as a function. Your apply filter function would be something like this:

    public function applyFilter(functionName:Function):void
    {
        listView.filterFunction = functionName;
        listView.refresh();
    }

Then your parent container of the list would have something like this:

public function myFilter(item:Object):Boolean{

}

private function callMyCustomListFilter():void
{
    myCustomList.applyFilter(myFilter);
}

---

I didn't notice you had the filter functions inside the list component. But, you can make them public and pass them in the same way:

    public function applyFilter(functionName:String):void
    {
        listView.filterFunction = functionName as Function // <-- THIS DOESN'T WORK;
        listView.refresh();
    }

    public function myFilter(obj:Object):Boolean
    {
        // Execution code
    }

    public function anotherFilter(obj:Object):Boolean
    {
        // Execution code
    }

]]>

And this:

<fx:Script>
<![CDATA[

    private function callMyCustomListFilter():void
    {
        myCustomList.applyFilter(myCustomList.myFilter);
    }

    ]]>

Answer 2

Perfect time to use bracket notation.

    public function applyFilter(functionName:String):void
    {
        listView.filterFunction = this[functionName]
        listView.refresh();
    }

You can also extend this with passing parameters if the need arises.

    public function applyFilter(functionName:String, arg1:String,arg2:Number):void
    {
        listView.filterFunction = this[functionName](arg1,arg2)
        listView.refresh();
    }

Answer 3

Okay to quickly answer your question, you are probably going to have to map your string functions to your filter functions. Something like this.

    public function applyFilter(functionName:String):void
    {
        var selectedFilterFunction:Function = null;
        if( functionName == 'myFilter' )
        {
             selectedFilterFunction = this.myFilter;
        }
        else if ( functionName == 'anotherFilter' )
        .....

        listView.filterFunction = selectedFilterFunction
        listView.refresh();
    }

You might even be able to get away this doing something like this.

listView.filterFunction = this[ fiterFunctionName ] as Function;

In any case I think you can glean what I am trying to say. You have to find the Function on your class as a property and then you can use it.

Another point you may want to consider is separating out that logic. Generally when I have a filter of some kind, I apply it in the model or the presenter depending on the basis of the filtering. I generally never filter in a view class.