How to make a variable in the WinJS.Namespace observable?

Question

I want to have some member of the global namespace "app" observable.

So I declare:

WinJS.Namespace.define("app", WinJS.Binding.as({
  bill: null
});

That gives me "app.bill === null". Now if I call "app.bill = new Bill()" it does not trigger any bound listeners.

Answer 1

Hi pkursawe,

The second parameter of the define function declares:

members

Type: object

The members of the new namespace.

 

Here you use a Binding, its definitely null without binding. Or you could do something like this:

WinJS.Namespace.define("app", {
    bill: WinJS.Binding.as({
        billCollection: someBillCollection,
    }),
});

bill.billCollection = xxx;

--James

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Answer 2

James, what you offer as solution is not the scenario I need. The namespaces app.bill needs to be observable by itself. It could be a string or an object, doesn't really matter. My use-case requires that when "app.bill" (the var, not the content!) changes, listeners of that object "app.bill" are triggered.

So "app.bill.amount = 1" is NOT my scenario. That works already. But I have UI elements that should not be shown when "app.bill" is null. So the UI elements bind to this property exactly like this:

<span data-win-bind="style.display:app.bill binding.displayIf">
  <span data-win-bind="textContent:app.bill.amount"></span>
</span>

My use-case is "app.bill = new Bill()" or "app.bill = null"