Flex is a complete set of tools to develop rich Internet cross-platform applications based on the Flash platform. With Flex, you can create applications that not only have the "wow factor" necessary to please clients and users alike, but the "usability factor" necessary to make your application a real success.

 Flex 2 has recently been released and can be downloaded at Adobe's Web site. This release includes Flex Builder 2 (an IDE based on Eclipse) and Flash Player 9. At Adobe's Web site, you'll also find tools specifically for ColdFusion such as the ColdFusion/Flex Connectivity package and ColdFusion extensions for Flex Builder. If you know how Flex 1.5 works, you'll be happy to hear that Flex 2 doesn't require a Flex server and that you can develop and deploy applications with Flex 2 for free using the Flex SDK (if you don't use the IDE).

A Flex application communicates to external services, and we find ColdFusion to be a perfect tool for providing those services. In this article, we'll walk you through the construction of an application with a Flex frontend and a ColdFusion backend. We believe that the integration with ColdFusion is so smooth you won't even notice you're transferring data from a remote server. The application you'll construct is a simple to-do list, but it will let us show you several Flex and ColdFusion features.

To start, you'll need the tools mentioned above, specifically Flex Builder IDE and the ColdFusion connectivity package and extensions downloaded and installed.

Setting Up Your Environment
The application will use a database with only one table, so you need to create a database with your favorite DBMS. This database should contain a table called "Task" with the following columns: id (varchar 35), description (varchar 1000), done (bit), and priority (smallint). Then register the data source in the CF administrator with the name "mytodolist."

Now you're ready to open Flex Builder and create a new project. While running the New Project wizard, specify that you'll be using ColdFusion Flash Remoting Services because the application will be communicating to your ColdFusion server via Flash Remoting rather than other alternatives such as XML or Web Services (see Figure 1). Assuming that you're running the development version on your local computer (http://localhost:8500), you can select "Use local ColdFusion server" in the second screen of the wizard. In the next screen enter "mytodolist" as the name of the project in the default location and finally, in the last screen, specify "http://localhost:8500/mytodolist/" as the Output folder URL.

The extensions you downloaded and installed include RDS support for viewing files and data sources. Make sure you have RDS enabled in your CF administrator and that you've set up the RDS preferences in Flex Builder. If your RDS connection is set up properly, you should be able to open the RDS Dataview (you can open it from Window > Other Views > RDS) and see the data source you created earlier (see Figure 2).

Running the ColdFusion Wizard
Another handy feature included in the ColdFusion extensions is the ability to run automatic generation of basic ColdFusion components. The "Create CFC" wizard will generate all the ColdFusion code you need for this application. Then you'll make a few changes to the components to meet specific needs. From the RDS Dataview, look for your data source ("mytodolist"), open the tables node, and right-click on the "Task" table to run the ColdFusion wizards > Create CFC option of the context menu (see Figure 3). This action will open a dialog that asks you what type of CFC you want and some other basic options. Make sure the CFC folder is your current project folder (mytodolist). Set the CFC package name to "mytodolist." Also check the option "The primary key is controlled by the user" because the component will set the id instead of letting the database choose the id. You also want to create an ActionScript value object that matches your Task CFC. So you need to check "Create an actionscript value object."

When you're finished, you should have three new files in your project: Task.cfc, TaskGateway.cfc, and Task.as.

Overview of the Application
The application consists of a list of undone tasks and a form to add a new task. Each task contains an icon that indicates its priority, a label that shows the description of the task, and a button that can mark the task done and remove it from the view. Figure 4 shows the finished application with styles applied.

To construct it, you'll use these components: VBox, Repeater, Panel, Button, Label, and form controls such as TextArea and ComboBox. You'll also create a custom component that will represent the view of each task item (TaskItem.mxml) and a custom component that will contain the edit form (EditForm.mxml). By creating custom components, you can reuse them throughout your application.

If you are wondering about the data, the application will get the list of tasks from a ColdFusion service and send requests to add new tasks and mark them as done.

Main Application File
The New Project wizard created an empty main application file called mytodolist.mxml. You'll use this file as the main canvas where you'll place the components and most of the ActionScript code. In a larger application, you will probably not want all your code in the same file, but for simplicity, you'll keep it there.

We have not yet described how to get the data from the server, but once the application gets the list of tasks, you'll need to store it in a local variable. To do that, declare the variable "tasks" inside a <mx:Script> block.

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

      [Bindable]
      private var tasks:ArrayCollection = null;
   ]]>
</mx:Script>

It's important to set this variable as "bindable" because you'll use it as the dataProvider of the repeater component.

In our layout, we want to have the list of tasks vertically positioned with one task below the other. By using a VBox component, we can add all the tasks and the VBox will position them how we want them. But the task list data will come from a ColdFusion service, so you don't know how many of them there'll be. So you'll use a repeater component that will "loop" over the collection of tasks and add them to the VBox.

<mx:VBox width="350">
<mx:Repeater dataProvider="{tasks}" id="taskList">
      <TaskItem taskData="{taskList.currentItem}" />
   </mx:Repeater>
</mx:VBox>

TaskItem Custom Component
If you save mytodolist.mxml file, you'll get an error indicating the TaskItem can't be resolved. This happens because we put the tag <TaskItem> inside the Repeater but the component TaskItem doesn't exist yet.

To create this custom component, you'll go to the File menu and click on New > MXML component. It will extend the Canvas and have 100% width because we want it to take the width of the parent container: the VBox. Save it as TaskItem.mxml.