Question

I’m using GWT overlay types to parse my JSON response form the web server. It all works fine, the problem is, if the required field doesn’t exist:

example:
JavaScriupt overlay type class

public class JSWorkplace extends JavaScriptObject{    
protected JSWorkplace() {        
}
public final native String getWidgets() /*-{
    return this.Widgets;
}-*/;

now if I have something like {“Widgets”:”Bla”} comes form the server everything is alright, getWidgets returns “Bla”.
If this “{}” comes from the server my application throws in the gwtWidgets function. How can I check if the field “Widgets” exists before reading it.

Regards,
Stefan

Answer 1

You can check if it’s undefined doing something like: this.Widgets == undefined.
Personally I prefer to set default values after the eval(). For example, in order to create your JSWorkplace object I would invoke a method like this:

public static native JSWorkspace createFromJSON(String json)/*-{
  var object = eval('(' + json + ')');
  if (object.Widgets == undefined) { object.Widgets = []; }

  ...

  return object;
}*-/;