Doubt in action script for Flex: getting unique elements from an ArrayCollection

Question

Hi,

I have an ArrayCollection as mentioned below.

        private var initDG:ArrayCollection = new ArrayCollection([
            {fact: "Order #2314", appName: "AA"},

            {fact: "Order #2315", appName: "BB"}

            {fact: "Order #2316", appName: "BB"}
                            ...

            {fact: "Order #2320", appName: "CC"}

            {fact: "Order #2321", appName: "CC"}

            ]);

I want to populate a ComboBox with UNIQUE VALUES of "appName" field from the ArrayCollection initDG.

<mx:ComboBox id="appCombo" dataProvider="{initDG}" labelField="appName"/>

One method I could think is to loop through the Array objects and for each object check and push unique appName entries into another Array. Is there any better solution available?

Answer 1

That sounds good to me:

var unique:Object = {};
var value:String;
var array:Array = initDG.toArray();
var result:Array = [];
var i:int = 0;
var n:int = array.length;
for (i; i < n; i++)
{
 value = array[i].appName;
 if (!unique[value])
 {
  unique[value] = true;
  result.push(value);
 }

}
return new ArrayCollection(result);

Answer 2

Alas, there is no unique() method in ActionScript's Array, but you can approximate it like this:

var names:Array = initDG.toArray().map(
    function (e:Object, i:Number, a:Array):String {
        return e.appName;
    }
);

var uniqueNames:Array = names.filter(
    function (name:String, i:Number, a:Array):Boolean {
                // Only returns true for the first instance.
        return names.indexOf(name) == i;
    }
);

Note this happens to work because you are filtering strings, which are compared by value. This wouldn't be effective if you needed to filter arbitrary objects.

Answer 3

you can used this class for finding unique arraycollection tempArray=_uniqueArray.applyUnqiueKey1(_normalsearchdata.toArray());

"uniqueArray" this is package name and _normalsearchdata is ArrayCollection;

package{ import mx.collections.ArrayCollection; public class applyUniqueKey{ private var tempArray:Array;

    private var tempIndex = 0;
    public var temp:String;
    public function applyUnqiueKey1(myArray)

    {
        tempArray = new Array();
        tempIndex = 0;  
        myArray.sort();
        tempArray[0] = myArray[0];
        tempIndex++;

        for(var i=1; i<myArray.length; i++) {
            if(myArray[i] != myArray[i-1]) {
                tempArray[tempIndex] = myArray[i];
                tempIndex++;
            }
        }
        var temp=String(tempArray.join());
        return new ArrayCollection(tempArray);
    }
}

}

Vijay