The value is not automatically passed to your widget, as this depends on your current context etc.
You will need to use the member names to retrieve the actual values (this also makes sure you have the newest values from memory/cache).
Try adding this:
update : function (ctxObj) {
var valueA = ctxObj.get(messageString);
var valueB = ctxObj.get(messageString_two);
var valueC = ctxObj.get(messageString_three);
}
Update is called automatically similar to postCreate. As soon as the widget receives the Context Object the update function is called.
You will also want to switch any rendering function calls that need this data to the 'update' function, otherwise it will probably render without data (postCreate is always called before update).