The one item issue with your HTTPService response XML data

It was an old problem that it happened again some days ago while supporting a client for a Flex 2 application.
You know that when you call the HTTPService class and it returns the response data, you can type casting them in ArrayCollection with the following code :

<mx:HTTPService id="myHS" url="data/states.xml"
   result="myAC = myHS.lastResult.dataroot.city as ArrayCollection" />

Now you're ready to use it in data binding with Flex 2 controls.
But if the response data returns an XML with only one item, you'll get the following error :

"cannot convert mx.utils::ObjectProxy@36fbf81 to mx.collections.ArrayCollection"

This is the sample response xml data:
<dataroot>
<city>
<id>22</id>
<region>TRENTINO ALTO ADIGE</region>
<city>TRENTO</city>
<population>449852</population>
</city>
</dataroot>

So you can use a result handler to better handle the error   :

<mx:HTTPService id="myHS" url="data/states.xml"
   result="resultHandler(event)" />

private function resultHandler(event :ResultEvent ) :void {

if( event.result.dataroot.city  == null ) {
mx.controls.Alert.show("The response data are empty !");
}
else if ( event.result.dataroot.city  is ObjectProxy ) {
// the response date has only one item
myAC =  new ArrayCollection( [event.result.dataroot.city  ] );
}
else {
myAC = event.result.dataroot.city   as ArrayCollection;

}
}

You cal also use the ArrayUtil.toArray() method to force the type conversion :

myAC  = new ArrayCollection(ArrayUtil.toArray(event.result.dataroot.city));

Hope that helps.
Thanks to Francesco for finding the solution on my old post, under comments ;)

Comments

[Matt]

Also I think resultFormat="array" will do the trick for you to force it into an array all the time.

[ajit parthan]

I have seen this problem when using WebService and resultFormat="object". And the workaround used is as mentioned in the post- check for ArrayCollection etc.

I have also found cases where the result is an Array even if there is only one object- but the XSD in both cases look exactly the same.

But given that the WebService is backed by a WSDL and XSD schema that defines the result format this feels more like a hack/workaround.

[Robert Stark]

I haven't had time to test this code with xml, but wouldn't this do it as well.

private function resultHandler(event :ResultEvent ) :void

{

var myAC:ArrayCollection;
if( event.result.dataroot.city  == null )
{
mx.controls.Alert.show("The response data are empty !");
}
else
{
myAC = new ArrayCollection(event.result.dataroot.city as Array);
}

}

[Marco Casario]

Thanks Matt ;) !

[Martin]

hey, this is a great post i have the same problem witch 1 item result, and i resolve with you code.

Grettins from Argentina.