AJAX - Return Arrays and Structs to your JavaScript with XML

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Functionality

The VDF AJAX Library provides the functionality for developers to call published methods within a WBO and receive a return value (for Functions). This is done using a Remote Method Invokation (RMI). Using RMI's for returning a single datatype is fairly straight-forward. If you want to return a Struct, Array , or an Array of Structs you need to do some more work. Remember, you are returning these datatypes to JavaScript and there is no direct translation from a Windows Struct or Array to a JavaScript Struct or Array.

The Solution

The solution is to return the data in an XML document. XML can be formatted to return a Struct of data, and Array, or an Array of Structs.


Calling the WBO Function from JavaScript

This is an example of a JavaScript function using the RMI to call a function of the webapp. It called the Function NameCasing of the oMyWBO. It passes a single argument of sName. When the Function returns, it will call the JavaScript method onNameCasing.

function nameCasing(sName) {
  var oRMI = new VdfRemoteMethodInvocation(true, "oMyWBO", "get_NameCasing", null, onNameCasing);
  oRMI.addParameter(sName);
  oRMI.sendCall();
}


Creating the XML in the WBO

1) create an XML document
2) add elements to the XML
3) get the memory address of the XML document
4) destroy the VDF connection to the address
5) return the memory address. This will return the XML document to the JavaScript

{ Published = True  }
{ Description = ""  }
Function NameCasing String sName Returns Address
  Handle hoRoot hoXML hoEvent
  Address aXml
  // create xml document
  Get Create U_cXMLDOMDocument                            to hoXML
  Set pbValidateOnParse of hoXML                          to False
  Get CreateDocumentElement of hoXML "response"           to hoRoot
  Send AddElement of hoRoot "lowercase" (lowercase(sName))
  Send AddElement of hoRoot "uppercase" (Uppercase(sName))
  Send AddElement of hoRoot "propercase" (Uppercase(Left(sName,1))+lowercase(Right(sName,(length(sName)-1))))
  Get paXml of hoXml to aXml
  Send Destroy of hoRoot
  Send Destroy of hoXML
  Function_Return aXML
End_Function   // NameChanges

Parsing the XML in JavaScript

1) check to see if there were any errors
2) make sure we have a return value
3) create the XML parser object
4) get the values from the XML

function onNameCasing(oRMI) {
  // If no errors
  if (oRMI.iErrorNumber==0){
    if (oRMI.sReturnValue!=null){
      // create XML parser
      try { // code for IE
        xmlDoc=new ActiveXObject("Microsoft.XMLDOM");
        xmlDoc.async="false";
        xmlDoc.loadXML(oRMI.sReturnValue);
      } catch(e) { // code for Mozilla, Firefox, Opera, etc.
        try {
          parser=new DOMParser();
          xmlDoc=parser.parseFromString(oRMI.sReturnValue,"text/xml");
        } catch(e) {
          alert(e.message);
          return;
        }
      }
    }
    if (xmlDoc!=null){
      var sLower="", sUpper="", sProper="";
      sLower=xmlDoc.getElementsByTagName("lowercase")[0].childNodes[0].nodeValue;
      sUpper=xmlDoc.getElementsByTagName("uppercase")[0].childNodes[0].nodeValue;
      sProper=xmlDoc.getElementsByTagName("propercase")[0].childNodes[0].nodeValue;
      //todo: do something with these values
    }
  }
}
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