Cannot access arrayCollection's children in datagrid

Question

Hi Guys,

I've got a Flex 3 application with an HTTPService returning an Atom feed. I catch the result from it and store it in an arrayCollection which is then the provider of my Datagrid. I have no problem accessing the data from the "first-level" of my Array, but cannot go under it. Not very clear, so here is some code:

My XML [part of it]:

<entry>
<title>Test 2</title>
<id>http://collaboration.*****.com/collaboration/messaging/feeds/****/todo//7D6637D3E86B3ED3C12575B***8479&lt;/id&gt;
<link rel="alternate" href="notes:///C12575B4004***8/0/7D6637D3E86B3ED3C12575B6004E8479" type="application/vnd.lotus-notes"/>
<published>2009-05-14T16:17:37+02:00</published>
<updated>2009-05-14T16:17:56+02:00</updated>
<clb:todo>
<clb:uid>7D66***3ED3C12575B6004E8479</clb:uid>
<clb:due>2009-05-31T12:01:00+02:00</clb:due>
<clb:status>Not Started</clb:status>
</clb:todo>
</entry>

My Datagrid Code:

  <mx:AdvancedDataGrid y="10" id="notesGrid" width="90%" height="243" designViewDataType="flat" x="10" selectionMode="multipleRows" dataProvider="{notesArray}" >
   <mx:columns>
    <mx:AdvancedDataGridColumn 
     headerText="TITRE" 
     dataField="title" 
     fontWeight="bold"
     />
    <mx:AdvancedDataGridColumn headerText="STATUT" dataField="todo.status"/>
   </mx:columns>
  </mx:AdvancedDataGrid>

The "title" column shows the data correctly, but the status column is empty ! When I launch my app in debug mode, I can see that my notesArray has the correct format and I can access todo -> status with the value...

I've been stuck on this for a few days, I'd appreciate any help ! Thanks and best regards !!

Answer 1

This could have something to do with the fact that the "status" node is using a different namespace "clb" than your title. You may need to specify the namespace in order to access it's data.

I had to do something similar when retrieving XML data from a .NET WebService. It took me a few days to figure it out.

If your XML looks like this:

<?xml version="1.0" encoding="utf-8"?>
<atomFeed xmlns:clb="CLB.data">
    <entry>
    <title>Test 2</title>
    <id>http://collaboration.*****.com/collaboration/messaging/feeds/****/todo//7D6637D3E86B3ED3C12575B***8479&lt;/id&gt;
    <link rel="alternate" href="notes:///C12575B4004***8/0/7D6637D3E86B3ED3C12575B6004E8479" type="application/vnd.lotus-notes"/>
    <published>2009-05-14T16:17:37+02:00</published>
    <updated>2009-05-14T16:17:56+02:00</updated>
    <clb:todo>
    <clb:uid>7D66***3ED3C12575B6004E8479</clb:uid>
    <clb:due>2009-05-31T12:01:00+02:00</clb:due>
    <clb:status>Not Started</clb:status>
    </clb:todo>
    </entry>
</atomFeed>

Add this to the ActionScript where you handle the HTTPService result:

private namespace clbNS = "CLB.data";

use namespace clbNS;

For example:

package { import mx.rpc.events.ResultEvent;

public class handleAtomFeed
{
    private namespace clbNS = "CLB.data";

    use namespace clbNS;

    private function resultHandler(event:ResultEvent):void
    {
        // pares the XML and build your ArrayCollection
    }
}

}

Give it shot, it just might work!!!

Answer 2

I'm pretty certain that the dataField property of DataGridColumn / AdvancedDataGridColumn doesn't automatically resolve nested properties, i.e. "todo.status"; you may want to try writing a labelFunction that will access the nested XML element for you.

Answer 3

A general rule I follow when it comes to problems of this sort is to do something like this (just to make sure that you are getting everything you are looking for):

import flash.utils.getQualifiedClassName;

// As a general rule, I don't find it the best idea to access an object in 
// an IList (ArrayCollection, XMLListCollection, et al ) by a dynamic property.
// Especially when they are coming from XML, the best way to access everything 
// is through getItemAt.
var len:int = todo.length;
for( var i:int = 0; i < len; i++ )
{
    var item:* = todo.getItemAt( i );
    trace( item, getQualifiedClassName( item ) );
}

After that, my first try would be replace this:

<mx:AdvancedDataGridColumn headerText="STATUT" dataField="todo.status"/>

with this:

<mx:AdvancedDataGridColumn headerText="STATUT" dataField="{ todo.status }"/>

Very often Flex does not play well with nested properties at all, but when you use the brackets, it gives the value which is found at that location as a more direct reference.

I think you are also better off using an XMLListCollection over an ArrayCollection. That way you can call children by name instead of relying on their normal index in the IList.