Tomás Lin’s Programming Brain Dump

Grails uses XPath in its XML converter, which requires additional processing in the Flex / ActionScript world. This post introduces a very simple solution that converts XML references into non-reference nodes.

This is a quick and dirty solution to a question posted by _HATES in the comments. Thanks for reading my blog.

The problem:

When you use Content Negotiation and the result has two references to the same item, Grails will render the second reference in an xml like the following:

<customer id=”1″>

<country reference=”/list/grill/grillvariations/grillVariation/customers/customer/country”/>

</customer>

ActionScript e4x lacks native support for the XPath format ( although there are external libraries like XPath-as3 that will do this for you).

For a recent project, I had to write my own resolver ( due to problems in SWF loading that affect ActionScript libraries ). Since this is something that might come up when you’re using Flex as a client for Grails, I thought I would share the funciton:

To use it, simply call:

var resolvedValue = xml ( fileWithAPotentialReference, GrailsResult );

private function xml(reference : XML, parentXML : XML) : XML {

  var resolved : XML = null;

  if ( reference!=null && reference.@id !=null &&  reference.@id.toString() != "") {

    resolved = reference;

  } else {

    var path : String = reference.@reference;

    var tokens : Array = path.split( "/" );

    var currentLocation : XML = parentXML;

    for each( var token : String in tokens ){

        var index : int = 0;

        if( token!= "" && token!="list"){

            if( token.indexOf("[") > 0 ) {

                var check : String = token.substr( token.indexOf("[")+1, token.indexOf("]")-1 );

                index = parseInt(check )-1;

                token = token.substr( 0, token.indexOf( "[" ));

             }

             var nextLocation:XML = currentLocation.elements(token)[index];

             if( nextLocation!= null ){

                currentLocation = nextLocation;

             }

          }
      }

    resolved = currentLocation;
  }

  return resolved;
}