Knockout Validation doesn't work on initial load if mapping plugin is called twice

Question

This one has been causing me grief for a while.

I have a web app that uses Knockout, Knockout Mapping, and Knockout Validation. Everything is going pretty well except for this problem. The problem is demonstrated by this Fiddle.

To demonstrate the problem, run the fiddle and then select something from the list. When it comes up, clear out the Name field. You may or may not see the validation message (it is random. On fiddle it seems never to show when first running but in my actual code, it sometimes does and sometimes doesn't when refreshing the page).

Now click on the reload button and do the same thing again. This time you should see the validation error.

Now for the really fun part. At the bottom of the javascript, comment out the line that says:

self.loadSupportData();

This is just to keep the second mapping from running. Try the experiment again. This time the validation will work on initial run.

What is causing this?

Cedric Cedric · Accepted Answer · 2012-10-05T09:55:07

I think your problem become because you load your datas before you apply your bindings.

Comment line :

self.loadData();

and modify last lines :

var viewModel = new PersonAttributeListViewModel();
ko.applyBindings(viewModel);
viewModel.loadData();

It works fine.

Knockout Validation doesn't work on initial load if mapping plugin is called twice

1 Answers