Flex 2 Developer's Guide > Building User Interfaces for
Flex Applications > Using Data Providers and Collections > Using IList interface methods and properties

Using IList interface methods and properties

The IList interface provides simple methods for indexed access to linear data. The interface provides a direct representation of the underlying data provider. Thus, any operation that changes the collection changes the data provider in a similar manner: if you insert a item as the third item in the collection, it also is the third item in the underlying data source.

NOTE

 

If you use the ICollectionView interface to sort or filter a collection, do not use the IList interface to manipulate the data, as the results are indeterminate.

The interface includes properties and methods that let you do the following:

You can use the IList interface methods and properties directly on any of the following classes or properties:

The following sample code uses an ArrayCollection object and its implementation of the IList interface methods to display an array of elements in a ComboBox control. For an example that uses IList interface methods to manage an ArrayCollection of objects with multiple fields, see Example: Modifying data in DataGrid control.

In the following example the Array data source initially consists of the following elements:

"AZ", "MA", "MZ", "MN", "MO", "MS"

When you click the Button control, the application uses the length property and several methods of the IList interface to do the following:

The code includes comments that describe the changes to the data provider.

<?xml version="1.0"?>
<!-- dpcontrols\UseIList.mxml -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
initialize="initData()">

    <mx:Script>
        <![CDATA[
            import mx.collections.*;

            // The data provider is an Array of Strings
            public var myArray:Array = ["AZ", "MA", "MZ", "MN", "MO", "MS"];
            // Declare an ArrayCollection that represents the Array.
            [Bindable]
            public var myAC:ArrayCollection;

            //Initialize the ArrayCollection.
            public function initData():void {
                myAC = new ArrayCollection(myArray); 
            }

            // The function to change the collection, and therefore
            // the Array.
            public function changeCollection():void {
                // Get the original collection length. 
                var oldLength:int=myAC.length;

                // Remove the invalid first item, AZ.
                var removedItem:String=String(myAC.removeItemAt(0));
                // Add ME as the second item. (ILists used 0-based indexing.)
                myAC.addItemAt("ME", 1);
                // Add MT at the end of the Array and collection.
                myAC.addItem("MT");
                // Change the third item from MZ to MI.
                myAC.setItemAt("MI", 2);
                // Get the updated collection length. 
                var newLength:int=myAC.length;
                // Get the index of the item with the value ME.
                var addedItemIndex:int=myAC.getItemIndex("ME");
                // Get the fifth item in the collection.
                var index4Item:String=String(myAC.getItemAt(4));

                // Display the information in the TextArea control.
                ta1.text="Start Length: " + oldLength + ". New Length: " +
                    newLength;
                ta1.text+=".\nRemoved " + removedItem;
                ta1.text+=".\nAdded ME at index " + addedItemIndex;
                ta1.text+=".\nThe item at index 4 is " + index4Item + ".";
                // Show that the base Array has been changed.
                ta1.text+="\nThe base Array is: " + myArray.join();
            }
        ]]>
    </mx:Script>

    <mx:ComboBox id="myCB" rowCount="7" dataProvider="{myAC}"/>
    <mx:TextArea id="ta1" height="75" width="300"/> 
    <mx:Button label="rearrange list" click="changeCollection();"/>
</mx:Application>

Flex 2.01

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