View source for AJAX - Return Arrays and Structs to your JavaScript with XML

= 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<br/>
2) add elements to the XML<br/>
3) get the memory address of the XML document<br/>
4) destroy the VDF connection to the address<br/>
5) return the memory address. This will return the XML document to the JavaScript<br/>

<source lang="dataflex">
 { 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
</source>

= Parsing the XML in JavaScript =

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

<source lang="js">
 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
     }
   }
 }
</source>

[[Category:Web Programming]]
[[Category:AJAX]]