Flex Filterfunction - Filter by Array of values

Question

How to filter an Arraycollection by "array of values" rather than a single value (simple comparision) , the below code snippet is for filtering by single value now I went into scenario like filter out only price [10,4,1,8] (some random values from the master collection). Is there any better way to do the second code snippet

Filter function simple comparision

            private function filterForTestData(item:Object):Boolean{
                   if(item.price < slider.value) return true;
                   else return false;      
            }

Filter by array of values

            private function filterForTestData(item:Object,filterBy:Array= [10,4,1,8]):Boolean{
                 for(randomprice in filterBy)
                 return item.price == randomprice;
}
[Edited]

Apply Filter

testData.filterFunction = filterForTestData;

[Edit]

One point I haven't mentioned is my items in the filterBy array are custom data not the basic datatypes.

shaunhusain · Accepted Answer · 2011-03-17 17:15:11Z

I was going to answer this saying use an object as a lookup then use hasOwnProperty to determine if the property is set on the filter Object. From actually testing my method along with these two (creating a mock set of data with strings of numbers (100,000 of them) and the variance between the methods in terms of run-time is negligble (ranges between 130 and 160ms). I think basically all three of these have the same running time.

Here's my full code so you can mess around and point out if I did something that invalidates my testing somehow but this seems to make sense to me, using indexOf it needs to iterate across the set until it finds the object (assuming a purely linear collection not a tree) same with hasOwnProperty (needs to get list of all properties and iterate across them, unless there's a mechanism built-in to find the property more efficiently:

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
                layout="vertical"
                height="100%"
                width="100%"
                xmlns:code="http://code.google.com/p/flex-iframe/"
                creationComplete="application1_creationCompleteHandler(event)">

    <mx:Script>
        <![CDATA[
            import flash.utils.getTimer;

            import mx.collections.ArrayCollection;
            import mx.events.FlexEvent;

             /* private function filterForTestData(item:Object):Boolean{
                return filterBy.hasOwnProperty(item);
            }  */
            /* private function filterForTestData(item:Object):Boolean{
                return filterBy.indexOf(item) != -1;
            } */
            private function filterForTestData(item:Object):Boolean{
                for(var randomprice in filterBy)
                    return item == randomprice;
                return false;
            }

            [Bindable]
            private var dp:ArrayCollection = new ArrayCollection(['1','2','3','4','5','6','7','8']);
            private var filterBy:Object={'10':true,'4':true,'1':true,'8':true};
            //private var filterBy:Array= ['10','4','1','8'];
            protected function button2_clickHandler(event:MouseEvent):void
            {
                // TODO Auto-generated method stub
                var startTime:int = getTimer();
                trace(getTimer());
                dp.filterFunction = filterForTestData;
                dp.refresh();
                var endTime:int = getTimer();
                trace("total time: " + (endTime-startTime).toString());
            }


            protected function application1_creationCompleteHandler(event:FlexEvent):void
            {
                // TODO Auto-generated method stub
                for(var i:int=0;i<100000;i++)
                {
                    dp.addItem(Math.floor(Math.random()*100).toString());
                }
                theList.dataProvider = dp;
            }

        ]]>
    </mx:Script>
    <mx:List id="theList" width="100"/>
    <mx:Button click="button2_clickHandler(event)"/>
</mx:Application>

I'm going to try and think this through from a pure data perspective and see if it's even possible to get better running time than this or if it's just the nature of the problem that necessitates a certain number of checks (asymptotic analysis).

Good question.

[Edit] Okay after thinking this through I believe without using a more complex data structure (and incurring the processor time cost up front in creating/re-organizing the data structure... thinking of keeping a balanced tree for search) I'm pretty sure any method will result in an equivalent or worse running time than these methods (that is linear running time or worse O(n)). Using a Tree structure you would get running times of O(log n) for search but incur more processing overhead in keeping the tree balanced (doing rotations as necessary). If anyone can invalidate this statement I would be happy if you did so, but I believe this is all true.

http://www.personal.kent.edu/~rmuhamma/Algorithms/MyAlgorithms/binarySearchTree.htm

bedwyr · Accepted Answer · 2011-03-17 16:19:37Z

1

Why not use the indexof method from Array?

private function filterForTestData(item:Object,filterBy:Array= [10,4,1,8]):Boolean{
    return filterBy.indexof(item.price) != -1;
}

(This checks to see if the item's price value is found in the filterBy array. If it is not, the indexof method returns -1. Otherwise, it will return the index of the array.)

I haven't tested this -- you might have to cast the item.price to a Number type, but I'm not certain.

answered Mar 17, 2011 at 16:19

bedwyr

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2 Comments

Sabha B Over a year ago

One point I haven't mentioned is my items in the filterBy array are custom data not the basic datatypes. Still indexof will work?

bedwyr Over a year ago

That's a good thing to note. I believe it will only work if the two objects being compared have the same reference (e.g. are the same object). The indexof method uses strict equality when searching for the search object's index: help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/….

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