Dashcode - how do you combine two values from one datasource - datasource

Question

In Dashcode, if I have a dataSource that has, for example, 2 fields called 'FirstName' and 'Last Name', how do I concatenate the 2 fields into one text field in a list view?
I'm fairly sure it must be to use a value transformer, so say that I assign the 'FirstName' field to the textfield, and add a value transformer... how do I then add the 'LastName' value to the 'value' variable in the transformer.
I'm sure it's to do with dashcode.getDataSource and valueForKeyPath and I think I'm close to the solution but it all seems a bit ungainly so any help would be much appreciated.

Answer 1

Correct - you need to use a Value Transformer.
In the Transformer, you would code as follows:
itemDescription = Class.create(DC.ValueTransformer,{
transformedValue: function(value){
var itemDataSource = dashcode.getDataSource('itemsList'); // The Data Source Name here
var lastName = itemDataSource.selection().valueForKey('lastName'); // Presumes you have a field called lastName
return value + " " + lastName;
}
});
Hope this helps - I battled with this for a day!!!

Answer 2

For future googlers, since there is absolutely no documentation anywhere about this :
When in detailed view to concatenate two fields from same the datasource :
XML
<?xml version="1.0" encoding="utf-8"?>
<immobilier>
<bien>
<ID>1453</ID>
<Titre>Maison / Villa F4</Titre>
<Ville>Sainte Clotilde</Ville>
<Quartier>BRETAGNE</Quartier>
</bien>
</immobilier>
To combine the fields Ville and Quartier create a value transformer like so :
mapAdresse = Class.create(DC.ValueTransformer,{
transformedValue: function(value){
if (value.trim() != "") {
//Replace immoListe with your source name
var itemDataSource = dashcode.getDataSource('immoListe');
//THIS IS THE MOST IMPORTANT : HOW TO FIND THE CURRENTLY SELECTED ITEM INDEX
var selectedIndex = document.getElementById('list').selectedIndex;
//Use the selectedIndex to find the record in the datasource
var quartier = itemDataSource.selection().valueForKey("bien")[selectedIndex].valueForKey("Quartier");
//Concatenate to your liking
if (quartier.trim() != "") value = value + ", "+ quartier;
}
return value;
}
});
Why is this not documented anywhere ?? Beats me !!