Uncaught TypeError: Cannot read property 'host' of undefined in Durandal when showing/closing modal dialog - durandal

Question

Using Durandal 2.0.1 (can't update to 2.1.0 yet due to restrictions on project development) and I have an intermittent issue with the error shown in this question title.
All I'm doing is defining a custom dialog box then showing it:
var pleaseWaitModal = new modalBusy();
dialog.show(pleaseWaitModal);
And when my ajax call is finished I do:
dialog.close(pleaseWaitModal);
...and then display another modal with the results of my ajax call.
This all works perfectly IF the ajax call takes half a second to a second. If it's a quicker call then I get Uncaught TypeError: Cannot read property 'host' of undefined in my console window. The box still closes, it's just that I get a panicky project manager asking what the red error is for...
Is this purely because I'm trying to run "dialog.close()" before "dialog.show()" has properly completed in some circumstances?
The sequence of events is basically:
*user instigates action requiring a detailed modal dialog to appear with data in it
*as it takes several seconds to populate on some occasions, an interim modal dialog is shown with "please wait" in it
*once the ajax request is complete, the "pleasewait" modal is closed and the "detail" modal is shown
*so a bit like:
var pleaseWaitModal = new modalBusy();
dialog.show(pleaseWaitModal);
//set up deferred calls for ajax data and call ...
var deferredAjax = callDataFunction(myparams...);
return deferredAjax.then(function(result) {
dialog.close(pleaseWaitModal);
var detailModal = new detailModal();
detailModal.show(result);
});
So I don't think I can achieve this using the promise on the dialog.show(pleaseWaitModal) call, can I?

Answer 1

Are you using the promise that is returned from the dialog.close function to open your new modal? You might try this:
From your initial dialog:
dialog.show(new modal()).then(function(responseData) {
dialog.show(new pleaseWaitModal(responseData));
});
I think the problem you're running into is async timing related, which is why using the deferred works so well.
EDIT: Related to my comment below, you might look at using only one modal, and putting a loading indicator inside of it, like so:
view.html
<div data-bind="visible: isLoading">
<h1>Please wait...</h1>
<i class="icon-spin icon-spinner icon-4x"></i>
</div>
modalViewModel.js
var vm = {
isLoading: ko.observable(true)
};
vm.activate = function() {
makeAjaxCall().then(function(data) {
vm.isLoading(false);
**Do whatever you need for your ajax return**
return true;
});
});
I think that should work for what you need as an alternative.