Flex (Learning Flex 3 Book) : Removing IEventDispatcher error from the DataGrid

When I decided to learn Flex I started with Learning Flex 3. It's a great book and does an excellent job of introducing the MXML framework and Flex Builder IDE. I would recommend it to anyone.

One of the problems I have with the book is it doesn't teach you how to remove warnings from your code. A later code example produces the following error: warning: unable to bind to property 'contact' on class 'XML' (class is not an IEventDispatcher). It's not a big deal, but I like to write code that doesn't produce hidden errors.

Here is the code from the book:

<mx: Application
    xmlns: mx="http: //www.adobe. com/2006/mxml"
    xmlns: view="com.oreilly.view.*"
    layout="absolute"
    applicationComplete="contactsService.send()" >
    <mx:HTTPService id="contactsService"
        resultFormat="e4x"
        url="contacts.xml" />
    <mx:DataGrid id="contactsDataGrid"
        dataProvider="{contactsService.lastResult.contact}"
        selectedIndex="0"
        left="10"
        top="10"
        bottom="10"
        width="300">
        <mx: columns>
            <mx: DataGridColumn headerText="First"  
            dataField="firstName"/>
            <mx: DataGridColumn headerText="Last" dataField="lastName"/>
        </mx:columns>
    </mx:DataGrid>
    <view: ContactViewer
        contact="{contactsDataGrid. selectedItem}"
        x="318" y="10">
    </view: ContactViewer>
</mx: Application>

The problem is the dataProvider property of DataGrid. It's unable to figure out how to parse the data, so it throws a warning. This can be resolved with casting. We can tell the dataProvider what it should be and it will remove the warning. Here is the code that will remove the warning.

dataProvider="{XMLList(XML(contactsService.lastResult).contact)}"

contactsService.lastResult is an XML object. There are multiple children in the object. We can then cast the XML object as an XMLList to use contact child node.

Feel free to leave a comment if you have any questions.

Flex: New Project Settings

When starting a new Flex project there are a few settings I like to use by default.

Changes to Flex Compiler
Flex Compiler options for a project can be found by right-clicking the project and selecting properties. Select Flex Compiler from the menu on the left. The following properties should be added to the Additional compiler arguments field.

When you're reading local xml files or image you might run into a sandbox security Error# 2140 or ReferenceError Error# 1069 using the HTTPService object. Use this switch to stop the error.
-use-network=false


The loading background color of a Flex app can be changed. Use this switch to change the property.
-default-background-color [HTML COLOR VALUE]
I typically use #FFFFFF.


Changes to the Application
I like to use a simple background for Flex apps. Add this property to the mx:Application to make the background white.
styleName="plain"