To achieve this why not use the spark data grid instead of a form? This way you add a new row to the data grid instead of adding controls for each parameter of sub object.

Lets take a look at an app that captures data for an expense report:

You can click on the trash icon to delete a row. And if you want to add blank rows, then you can either click on the new icon in the top left of the grid or click the TAB key in the comments field of the last row.

I primarily did the following customization to change the look of the datagrid:

• Custom skin for the datagrid (EntryDGSkin.mxml) to hide all the row and column separators.
• Used custom item renderers and marked rendererIsEditable as true so the controls are always visible when the rows are present in the datagrid

There are validators defined inside the item renderer and when the validation fails the item renderer changes a boolean property (invalidValue) on the parent document. So before saving, the document checks the boolean value to decide whether to proceed with save or not. If you don’t like the approach to set a boolean flag, then you can also access each validator via the itemRenderer for a particular cell. To access the itemRender use the getItemRendererAt() method present on grid property inside the spark data grid.

Also you should pay attention to the prepare()and discard()methods inside the data grid itemRenderers. The prepare() method is called for every visual update and it sets the data to the sub component of item renderer. I am using a boolean flag (pendingEdits – set to false when there are unsaved changes) inside the itemRenderers to decide whether to update the sub component or not.

Spark datagrid is a new feature in Flex SDK 4.5 and to import the fxp file you would need Flash Builder 4.5.
Both Flex SDK 4.5 and Flash Builder 4.5 were announced recently. See the flex team blog

Feedback is welcome

Prerequisites:

• Debug version of Flash Player
• SWF file that has been compiled in debug mode
• The preloaded SWF must be local trusted.

Following is how you can ensure that the prerequisites are being met and possible resolutions:

I. To ensure that you are using the debug version of flash player, you can simply compile and run the following mxml code and it should list the version and also if it supports debugging or not:

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="horizontal" creationComplete="application1_creationCompleteHandler(event)">
	<mx:Script>
		<![CDATA[
			import mx.events.FlexEvent;
			protected function application1_creationCompleteHandler(event:FlexEvent):void
			{
				playerVersion.text = Capabilities.version;
				isDebugger.text = String(Capabilities.isDebugger);
			}
		]]>
	</mx:Script>
	<mx:Label text="Version"/><mx:Label id="playerVersion"/><mx:Label text="Supports Debugging? "/><mx:Label id="isDebugger"/>
</mx:Application>

Resolution: Reinstall debug version of flash player.

II. To ensure that you are using the debug version of the SWF, you can run swfdump on the swf file. The swfdump generates an XML report. Look for tags like EnableDebugger2 and DebugID in the report. If these tags are missing then you are probably running a release mode swf.

Resolution: Recompile SWF with debug info. To do this from command line add -debug=true to mxmlc command. To do this from Flash builder, make sure debug is not set to false in additional compiler arguments or a local config file.

III. To ensure that PreloadSwf is local trusted, you can follow the following steps:

1. Run tail -f command on the mm.cfg file and then click the start button in code coverage plug-in.
   The mm.cfg file is present at the following location:

   XP: C:\Documents and Settings\username
   Vista/Win7: C:\Users\username
   Mac: /home/username or if that doesn’t exist: /Library/Application Support/Macromedia

   After you click the start button, the plugin should add a PreloadSwf entry to the mm.cfg file. If it doesn’t then you should make sure that mm.cfg is writable and that the user has permissions.

   An example of PreloadSwf entry:
   PreloadSwf=/Users/username/Documents/Adobe Flash Builder 4/.metadata/.plugins/com.adobe.flash.codecoverage/CodeCoverageAgent.swf?host=localhost&port=9900&level=0

   Note down the absolute path of folder containing CodeCoverageAgent.swf. It should be in your FB workspace at <workspace>/.metadata/.plugins/com.adobe.flash.codecoverage

   Also the plug-in removes the PreloadSwf entry when you click the stop button

2. Inspect at the trust files.
   Location of trust file (per-user):
   XP C:\Documents and Settings\username\Application Data\Macromedia\Flash Player\#Security\FlashPlayerTrust
   Vista/Win7: C:\Users\username\AppData\Roaming\Macromedia\Flash Player\#Security\FlashPlayerTrust
   Mac: /Users/username/Library/Preferences/Macromedia/Flash Player/#Security/FlashPlayerTrust

   Location of trust file (global):
   XP/Vista/Win7 C:\WINDOWS\system32\Macromed\Flash\FlashPlayerTrust
   Mac /Library/Application Support/Macromedia/FlashPlayerTrust

   The trust file is usually called flashbuilder.cfg. Make sure that the path of folder containing CodeCoverageAgent.swf is present in the trust file.

Resolution: Add parent folder of CodeCoverageAgent.swf to the trust file. If the trust file is not present create a new trust file. Also it is important to restart your browser/AIR after changes to the trust file.

If all the prerequisites are being satisfied then make sure that the port number (9900) is free for use by code coverage plug-in. In case 9900 is not available then you should update the port number in the code coverage preferences.

For documentation related to the tool you can go here

This tool allows for the following:

• Choose between line and/or method level coverage
• Apply filters on the view – so you can hide packages in which you are not interested
• Save detailed reports – so you can view them later and compare with other coverage reports for your code base
• Export high level coverage summary – This is a csv based summary of coverage for your code base

When you save a detailed report, it creates two files on your system .ascc and .ascs. The .ascs file is a compressed file that contains the sources on which the coverage was performed. So if you want another engineers on your team to look at the coverage data, just give them the two files and they won’t need to sync to the sources on their computer (because the sources for the report will come from .ascs file).

It can even be used to perform code coverage for more than one applications at the same time (may be you have a library or framework for which you have a ton of test cases).

I encourage you to try the tool, and if you have any questions or feedback please use the forum.